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 $53.96   13.237%   $61.1027   $61.10   $61.10   $61.10  
  Purchase #2 $68.82   3.600%   $71.2975   $71.30   $71.30   $71.30  
  Purchase #3 $198.67   8.318%   $215.1954   $215.20   $215.20   $215.20  
  Purchase #4 $102.32   13.759%   $116.3982   $116.40   $116.40   $116.40  
  Purchase #5 $206.35   9.656%   $226.2752   $226.28   $226.30   $226.30  
  Purchase #6 $94.93   11.297%   $105.6542   $105.65   $105.65   $105.70  
  Purchase #7 $241.71   12.343%   $271.5443   $271.54   $271.55   $271.50  
  7 purchase totals = $966.76       $1,067.4675   $1,067.47   $1,067.50   $1,067.50