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 $219.31   12.426%   $246.5615   $246.56   $246.55   $246.60  
  Purchase #2 $234.39   4.289%   $244.443   $244.44   $244.45   $244.40  
  Purchase #3 $60.91   8.663%   $66.1866   $66.19   $66.20   $66.20  
  Purchase #4 $222.39   4.466%   $232.3219   $232.32   $232.30   $232.30  
  Purchase #5 $171.56   5.699%   $181.3372   $181.34   $181.35   $181.30  
  Purchase #6 $113.61   3.633%   $117.7375   $117.74   $117.75   $117.70  
  Purchase #7 $31.81   12.315%   $35.7274   $35.73   $35.75   $35.70  
  7 purchase totals = $1,053.98       $1,124.3151   $1,124.32   $1,124.35   $1,124.20