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 $193.41   5.851%   $204.7264   $204.73   $204.75   $204.70  
  Purchase #2 $54.97   11.271%   $61.1657   $61.17   $61.15   $61.20  
  Purchase #3 $116.44   12.870%   $131.4258   $131.43   $131.45   $131.40  
  Purchase #4 $217.96   9.339%   $238.3153   $238.32   $238.30   $238.30  
  Purchase #5 $150.94   7.651%   $162.4884   $162.49   $162.50   $162.50  
  Purchase #6 $68.54   12.761%   $77.2864   $77.29   $77.30   $77.30  
  Purchase #7 $73.58   7.547%   $79.1331   $79.13   $79.15   $79.10  
  7 purchase totals = $875.84       $954.5411   $954.56   $954.60   $954.50