Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $201.29   10.846%   $223.1219   $223.12   $223.10   $223.10  
  Purchase #2 $244.93   9.387%   $267.9216   $267.92   $267.90   $267.90  
  Purchase #3 $98.57   13.244%   $111.6246   $111.62   $111.60   $111.60  
  Purchase #4 $234.28   9.530%   $256.6069   $256.61   $256.60   $256.60  
  Purchase #5 $203.82   13.273%   $230.873   $230.87   $230.85   $230.90  
  Purchase #6 $197.85   4.407%   $206.5692   $206.57   $206.55   $206.60  
  Purchase #7 $167.46   6.712%   $178.6999   $178.70   $178.70   $178.70  
  7 purchase totals = $1,348.20       $1,475.4171   $1,475.41   $1,475.30   $1,475.40