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 $147.53   10.233%   $162.6267   $162.63   $162.65   $162.60  
  Purchase #2 $113.95   7.402%   $122.3846   $122.38   $122.40   $122.40  
  Purchase #3 $59.28   8.183%   $64.1309   $64.13   $64.15   $64.10  
  Purchase #4 $181.29   12.385%   $203.7428   $203.74   $203.75   $203.70  
  Purchase #5 $48.60   6.874%   $51.9408   $51.94   $51.95   $51.90  
  Purchase #6 $244.82   4.824%   $256.6301   $256.63   $256.65   $256.60  
  Purchase #7 $193.93   9.864%   $213.0593   $213.06   $213.05   $213.10  
  7 purchase totals = $989.40       $1,074.5152   $1,074.51   $1,074.60   $1,074.40