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 $56.49   12.172%   $63.366   $63.37   $63.35   $63.40  
  Purchase #2 $105.94   5.202%   $111.451   $111.45   $111.45   $111.50  
  Purchase #3 $129.97   3.528%   $134.5553   $134.56   $134.55   $134.60  
  Purchase #4 $58.86   6.761%   $62.8395   $62.84   $62.85   $62.80  
  Purchase #5 $197.46   8.107%   $213.4681   $213.47   $213.45   $213.50  
  Purchase #6 $69.76   6.545%   $74.3258   $74.33   $74.35   $74.30  
  Purchase #7 $95.43   7.692%   $102.7705   $102.77   $102.75   $102.80  
  7 purchase totals = $713.91       $762.7762   $762.79   $762.75   $762.90