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 $192.71   12.272%   $216.3594   $216.36   $216.35   $216.40  
  Purchase #2 $232.65   4.711%   $243.6101   $243.61   $243.60   $243.60  
  Purchase #3 $231.95   12.837%   $261.7254   $261.73   $261.75   $261.70  
  Purchase #4 $82.79   5.187%   $87.0843   $87.08   $87.10   $87.10  
  Purchase #5 $248.30   7.849%   $267.7891   $267.79   $267.80   $267.80  
  Purchase #6 $167.40   7.655%   $180.2145   $180.21   $180.20   $180.20  
  Purchase #7 $167.81   12.859%   $189.3887   $189.39   $189.40   $189.40  
  7 purchase totals = $1,323.61       $1,446.1715   $1,446.17   $1,446.20   $1,446.20