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 $235.62   13.586%   $267.6313   $267.63   $267.65   $267.60  
  Purchase #2 $86.61   10.377%   $95.5975   $95.60   $95.60   $95.60  
  Purchase #3 $107.87   4.773%   $113.0186   $113.02   $113.00   $113.00  
  Purchase #4 $35.90   5.156%   $37.751   $37.75   $37.75   $37.80  
  Purchase #5 $247.78   11.616%   $276.5621   $276.56   $276.55   $276.60  
  Purchase #6 $209.84   5.484%   $221.3476   $221.35   $221.35   $221.30  
  Purchase #7 $45.93   7.490%   $49.3702   $49.37   $49.35   $49.40  
  7 purchase totals = $969.55       $1,061.2783   $1,061.28   $1,061.25   $1,061.30