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 $174.83   11.456%   $194.8585   $194.86   $194.85   $194.90  
  Purchase #2 $230.54   6.238%   $244.9211   $244.92   $244.90   $244.90  
  Purchase #3 $166.64   4.421%   $174.0072   $174.01   $174.00   $174.00  
  Purchase #4 $189.29   9.615%   $207.4902   $207.49   $207.50   $207.50  
  Purchase #5 $157.51   6.873%   $168.3357   $168.34   $168.35   $168.30  
  Purchase #6 $135.80   11.592%   $151.5419   $151.54   $151.55   $151.50  
  Purchase #7 $60.56   5.758%   $64.047   $64.05   $64.05   $64.00  
  7 purchase totals = $1,115.17       $1,205.2016   $1,205.21   $1,205.20   $1,205.10