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 $119.61   5.600%   $126.3082   $126.31   $126.30   $126.30  
  Purchase #2 $226.84   3.842%   $235.5552   $235.56   $235.55   $235.60  
  Purchase #3 $63.43   7.369%   $68.1042   $68.10   $68.10   $68.10  
  Purchase #4 $147.99   5.597%   $156.273   $156.27   $156.25   $156.30  
  Purchase #5 $96.31   5.273%   $101.3884   $101.39   $101.40   $101.40  
  Purchase #6 $183.97   12.263%   $206.5302   $206.53   $206.55   $206.50  
  Purchase #7 $88.54   3.612%   $91.7381   $91.74   $91.75   $91.70  
  7 purchase totals = $926.69       $985.8973   $985.90   $985.90   $985.90