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 $199.31   3.341%   $205.9689   $205.97   $205.95   $206.00  
  Purchase #2 $234.84   4.817%   $246.1522   $246.15   $246.15   $246.20  
  Purchase #3 $14.80   12.131%   $16.5954   $16.60   $16.60   $16.60  
  Purchase #4 $136.85   6.553%   $145.8178   $145.82   $145.80   $145.80  
  Purchase #5 $150.96   12.550%   $169.9055   $169.91   $169.90   $169.90  
  Purchase #6 $182.43   6.305%   $193.9322   $193.93   $193.95   $193.90  
  Purchase #7 $184.38   10.577%   $203.8819   $203.88   $203.90   $203.90  
  7 purchase totals = $1,103.57       $1,182.2539   $1,182.26   $1,182.25   $1,182.30