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 $213.52   13.282%   $241.8797   $241.88   $241.90   $241.90  
  Purchase #2 $25.43   6.572%   $27.1013   $27.10   $27.10   $27.10  
  Purchase #3 $129.33   4.303%   $134.8951   $134.90   $134.90   $134.90  
  Purchase #4 $16.91   6.540%   $18.0159   $18.02   $18.00   $18.00  
  Purchase #5 $203.44   3.308%   $210.1698   $210.17   $210.15   $210.20  
  Purchase #6 $226.30   8.145%   $244.7321   $244.73   $244.75   $244.70  
  Purchase #7 $61.45   10.224%   $67.7326   $67.73   $67.75   $67.70  
  7 purchase totals = $876.38       $944.5265   $944.53   $944.55   $944.50