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 $65.87   7.707%   $70.9466   $70.95   $70.95   $70.90  
  Purchase #2 $190.27   5.741%   $201.1934   $201.19   $201.20   $201.20  
  Purchase #3 $187.63   11.594%   $209.3838   $209.38   $209.40   $209.40  
  Purchase #4 $66.64   8.786%   $72.495   $72.50   $72.50   $72.50  
  Purchase #5 $248.25   11.200%   $276.054   $276.05   $276.05   $276.10  
  Purchase #6 $105.99   12.707%   $119.4581   $119.46   $119.45   $119.50  
  Purchase #7 $85.82   7.188%   $91.9887   $91.99   $92.00   $92.00  
  7 purchase totals = $950.47       $1,041.5196   $1,041.52   $1,041.55   $1,041.60