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 $211.71   10.621%   $234.1957   $234.20   $234.20   $234.20  
  Purchase #2 $163.91   3.107%   $169.0027   $169.00   $169.00   $169.00  
  Purchase #3 $18.43   11.791%   $20.6031   $20.60   $20.60   $20.60  
  Purchase #4 $106.54   11.119%   $118.3862   $118.39   $118.40   $118.40  
  Purchase #5 $136.65   12.183%   $153.2981   $153.30   $153.30   $153.30  
  Purchase #6 $232.43   10.387%   $256.5725   $256.57   $256.55   $256.60  
  Purchase #7 $247.95   3.287%   $256.1001   $256.10   $256.10   $256.10  
  7 purchase totals = $1,117.62       $1,208.1584   $1,208.16   $1,208.15   $1,208.20