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 $48.67   3.621%   $50.4323   $50.43   $50.45   $50.40  
  Purchase #2 $240.96   8.862%   $262.3139   $262.31   $262.30   $262.30  
  Purchase #3 $188.27   10.599%   $208.2247   $208.22   $208.20   $208.20  
  Purchase #4 $231.42   5.735%   $244.6919   $244.69   $244.70   $244.70  
  Purchase #5 $83.60   6.363%   $88.9195   $88.92   $88.90   $88.90  
  Purchase #6 $124.64   8.663%   $135.4376   $135.44   $135.45   $135.40  
  Purchase #7 $19.72   4.747%   $20.6561   $20.66   $20.65   $20.70  
  7 purchase totals = $937.28       $1,010.6760   $1,010.67   $1,010.65   $1,010.60