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 $184.43   5.526%   $194.6216   $194.62   $194.60   $194.60  
  Purchase #2 $169.35   7.447%   $181.9615   $181.96   $181.95   $182.00  
  Purchase #3 $189.30   11.110%   $210.3312   $210.33   $210.35   $210.30  
  Purchase #4 $199.26   13.207%   $225.5763   $225.58   $225.60   $225.60  
  Purchase #5 $142.27   6.550%   $151.5887   $151.59   $151.60   $151.60  
  Purchase #6 $148.38   3.192%   $153.1163   $153.12   $153.10   $153.10  
  Purchase #7 $229.26   3.381%   $237.0113   $237.01   $237.00   $237.00  
  7 purchase totals = $1,262.25       $1,354.2069   $1,354.21   $1,354.20   $1,354.20