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 $58.88   7.427%   $63.253   $63.25   $63.25   $63.30  
  Purchase #2 $211.93   5.794%   $224.2092   $224.21   $224.20   $224.20  
  Purchase #3 $209.32   3.166%   $215.9471   $215.95   $215.95   $215.90  
  Purchase #4 $241.30   7.232%   $258.7508   $258.75   $258.75   $258.80  
  Purchase #5 $6.42   10.482%   $7.0929   $7.09   $7.10   $7.10  
  Purchase #6 $108.84   7.401%   $116.8952   $116.90   $116.90   $116.90  
  Purchase #7 $149.54   12.238%   $167.8407   $167.84   $167.85   $167.80  
  7 purchase totals = $986.23       $1,053.9889   $1,053.99   $1,054.00   $1,054.00