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 $214.59   12.847%   $242.1584   $242.16   $242.15   $242.20  
  Purchase #2 $211.68   6.534%   $225.5112   $225.51   $225.50   $225.50  
  Purchase #3 $69.92   7.664%   $75.2787   $75.28   $75.30   $75.30  
  Purchase #4 $217.57   13.344%   $246.6025   $246.60   $246.60   $246.60  
  Purchase #5 $142.78   11.739%   $159.5409   $159.54   $159.55   $159.50  
  Purchase #6 $52.30   8.492%   $56.7413   $56.74   $56.75   $56.70  
  Purchase #7 $133.75   9.291%   $146.1767   $146.18   $146.20   $146.20  
  7 purchase totals = $1,042.59       $1,152.0097   $1,152.01   $1,152.05   $1,152.00