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 $82.51   13.467%   $93.6216   $93.62   $93.60   $93.60  
  Purchase #2 $50.62   13.407%   $57.4066   $57.41   $57.40   $57.40  
  Purchase #3 $121.60   3.277%   $125.5848   $125.58   $125.60   $125.60  
  Purchase #4 $177.59   11.103%   $197.3078   $197.31   $197.30   $197.30  
  Purchase #5 $14.85   8.277%   $16.0791   $16.08   $16.10   $16.10  
  Purchase #6 $122.75   4.316%   $128.0479   $128.05   $128.05   $128.00  
  Purchase #7 $132.51   9.109%   $144.5803   $144.58   $144.60   $144.60  
  7 purchase totals = $702.43       $762.6281   $762.63   $762.65   $762.60