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 $88.49   6.456%   $94.2029   $94.20   $94.20   $94.20  
  Purchase #2 $216.56   13.200%   $245.1459   $245.15   $245.15   $245.10  
  Purchase #3 $174.55   12.280%   $195.9847   $195.98   $196.00   $196.00  
  Purchase #4 $95.96   11.803%   $107.2862   $107.29   $107.30   $107.30  
  Purchase #5 $149.89   3.857%   $155.6713   $155.67   $155.65   $155.70  
  Purchase #6 $58.51   5.133%   $61.5133   $61.51   $61.50   $61.50  
  Purchase #7 $54.97   13.788%   $62.5493   $62.55   $62.55   $62.50  
  7 purchase totals = $838.93       $922.3536   $922.35   $922.35   $922.30