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 $87.44   8.639%   $94.9939   $94.99   $95.00   $95.00  
  Purchase #2 $103.31   7.646%   $111.2091   $111.21   $111.20   $111.20  
  Purchase #3 $139.28   10.644%   $154.105   $154.11   $154.10   $154.10  
  Purchase #4 $27.43   8.594%   $29.7873   $29.79   $29.80   $29.80  
  Purchase #5 $132.53   13.262%   $150.1061   $150.11   $150.10   $150.10  
  Purchase #6 $219.98   8.464%   $238.5991   $238.60   $238.60   $238.60  
  Purchase #7 $204.49   9.407%   $223.7264   $223.73   $223.75   $223.70  
  7 purchase totals = $914.46       $1,002.5269   $1,002.54   $1,002.55   $1,002.50