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 $112.98   8.571%   $122.6635   $122.66   $122.65   $122.70  
  Purchase #2 $235.40   4.655%   $246.3579   $246.36   $246.35   $246.40  
  Purchase #3 $230.40   9.794%   $252.9654   $252.97   $252.95   $253.00  
  Purchase #4 $14.75   9.455%   $16.1446   $16.14   $16.15   $16.10  
  Purchase #5 $207.69   4.355%   $216.7349   $216.73   $216.75   $216.70  
  Purchase #6 $194.37   5.415%   $204.8951   $204.90   $204.90   $204.90  
  Purchase #7 $14.44   13.132%   $16.3363   $16.34   $16.35   $16.30  
  7 purchase totals = $1,010.03       $1,076.0977   $1,076.10   $1,076.10   $1,076.10