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 $63.33   11.695%   $70.7364   $70.74   $70.75   $70.70  
  Purchase #2 $158.31   11.404%   $176.3637   $176.36   $176.35   $176.40  
  Purchase #3 $123.94   6.824%   $132.3977   $132.40   $132.40   $132.40  
  Purchase #4 $192.30   7.436%   $206.5994   $206.60   $206.60   $206.60  
  Purchase #5 $122.56   3.172%   $126.4476   $126.45   $126.45   $126.40  
  Purchase #6 $211.68   8.281%   $229.2092   $229.21   $229.20   $229.20  
  Purchase #7 $8.64   5.749%   $9.1367   $9.14   $9.15   $9.10  
  7 purchase totals = $880.76       $950.8907   $950.90   $950.90   $950.80