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 $72.97   4.572%   $76.3062   $76.31   $76.30   $76.30  
  Purchase #2 $31.49   10.788%   $34.8871   $34.89   $34.90   $34.90  
  Purchase #3 $148.99   12.418%   $167.4916   $167.49   $167.50   $167.50  
  Purchase #4 $227.39   10.775%   $251.8913   $251.89   $251.90   $251.90  
  Purchase #5 $54.78   9.451%   $59.9573   $59.96   $59.95   $60.00  
  Purchase #6 $201.84   5.258%   $212.4527   $212.45   $212.45   $212.50  
  Purchase #7 $217.59   11.201%   $241.9623   $241.96   $241.95   $242.00  
  7 purchase totals = $955.05       $1,044.9485   $1,044.95   $1,044.95   $1,045.10