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 $191.53   11.756%   $214.0463   $214.05   $214.05   $214.00  
  Purchase #2 $244.54   8.300%   $264.8368   $264.84   $264.85   $264.80  
  Purchase #3 $242.27   9.485%   $265.2493   $265.25   $265.25   $265.20  
  Purchase #4 $22.42   7.562%   $24.1154   $24.12   $24.10   $24.10  
  Purchase #5 $163.98   10.168%   $180.6535   $180.65   $180.65   $180.70  
  Purchase #6 $183.87   12.554%   $206.953   $206.95   $206.95   $207.00  
  Purchase #7 $52.97   5.152%   $55.699   $55.70   $55.70   $55.70  
  7 purchase totals = $1,101.58       $1,211.5533   $1,211.56   $1,211.55   $1,211.50