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 $59.76   6.543%   $63.6701   $63.67   $63.65   $63.70  
  Purchase #2 $169.45   10.538%   $187.3066   $187.31   $187.30   $187.30  
  Purchase #3 $43.81   11.754%   $48.9594   $48.96   $48.95   $49.00  
  Purchase #4 $102.73   4.609%   $107.4648   $107.46   $107.45   $107.50  
  Purchase #5 $219.43   12.633%   $247.1506   $247.15   $247.15   $247.20  
  Purchase #6 $243.85   9.476%   $266.9572   $266.96   $266.95   $267.00  
  Purchase #7 $217.67   9.423%   $238.181   $238.18   $238.20   $238.20  
  7 purchase totals = $1,056.70       $1,159.6897   $1,159.69   $1,159.65   $1,159.90