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 $113.86   4.495%   $118.978   $118.98   $119.00   $119.00  
  Purchase #2 $156.37   11.246%   $173.9554   $173.96   $173.95   $174.00  
  Purchase #3 $60.57   7.790%   $65.2884   $65.29   $65.30   $65.30  
  Purchase #4 $228.31   8.105%   $246.8145   $246.81   $246.80   $246.80  
  Purchase #5 $107.92   7.816%   $116.355   $116.36   $116.35   $116.40  
  Purchase #6 $210.82   5.218%   $221.8206   $221.82   $221.80   $221.80  
  Purchase #7 $185.98   6.451%   $197.9776   $197.98   $198.00   $198.00  
  7 purchase totals = $1,063.83       $1,141.1895   $1,141.20   $1,141.20   $1,141.30