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 $64.33   11.711%   $71.8637   $71.86   $71.85   $71.90  
  Purchase #2 $227.37   7.748%   $244.9866   $244.99   $245.00   $245.00  
  Purchase #3 $135.69   11.373%   $151.122   $151.12   $151.10   $151.10  
  Purchase #4 $211.85   11.654%   $236.539   $236.54   $236.55   $236.50  
  Purchase #5 $187.76   13.683%   $213.4512   $213.45   $213.45   $213.50  
  Purchase #6 $188.65   11.590%   $210.5145   $210.51   $210.50   $210.50  
  Purchase #7 $45.68   5.635%   $48.2541   $48.25   $48.25   $48.30  
  7 purchase totals = $1,061.33       $1,176.7311   $1,176.72   $1,176.70   $1,176.80