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 $66.75   11.260%   $74.2661   $74.27   $74.25   $74.30  
  Purchase #2 $83.91   11.305%   $93.396   $93.40   $93.40   $93.40  
  Purchase #3 $90.32   10.192%   $99.5254   $99.53   $99.55   $99.50  
  Purchase #4 $226.69   4.532%   $236.9636   $236.96   $236.95   $237.00  
  Purchase #5 $141.92   10.343%   $156.5988   $156.60   $156.60   $156.60  
  Purchase #6 $187.40   8.237%   $202.8361   $202.84   $202.85   $202.80  
  Purchase #7 $218.67   12.844%   $246.756   $246.76   $246.75   $246.80  
  7 purchase totals = $1,015.66       $1,110.3420   $1,110.36   $1,110.35   $1,110.40