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 $208.32   13.160%   $235.7349   $235.73   $235.75   $235.70  
  Purchase #2 $98.49   6.138%   $104.5353   $104.54   $104.55   $104.50  
  Purchase #3 $50.63   7.109%   $54.2293   $54.23   $54.25   $54.20  
  Purchase #4 $201.90   3.311%   $208.5849   $208.58   $208.60   $208.60  
  Purchase #5 $57.83   5.199%   $60.8366   $60.84   $60.85   $60.80  
  Purchase #6 $157.85   8.317%   $170.9784   $170.98   $171.00   $171.00  
  Purchase #7 $99.53   7.297%   $106.7927   $106.79   $106.80   $106.80  
  7 purchase totals = $874.55       $941.6921   $941.69   $941.80   $941.60