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 $53.47   8.396%   $57.9593   $57.96   $57.95   $58.00  
  Purchase #2 $138.78   10.217%   $152.9592   $152.96   $152.95   $153.00  
  Purchase #3 $80.79   3.269%   $83.431   $83.43   $83.45   $83.40  
  Purchase #4 $163.45   4.135%   $170.2087   $170.21   $170.20   $170.20  
  Purchase #5 $20.25   10.874%   $22.452   $22.45   $22.45   $22.50  
  Purchase #6 $221.61   10.276%   $244.3826   $244.38   $244.40   $244.40  
  Purchase #7 $71.72   4.739%   $75.1188   $75.12   $75.10   $75.10  
  7 purchase totals = $750.07       $806.5116   $806.51   $806.50   $806.60