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 $101.70   5.184%   $106.9721   $106.97   $106.95   $107.00  
  Purchase #2 $25.50   8.433%   $27.6504   $27.65   $27.65   $27.70  
  Purchase #3 $40.95   5.259%   $43.1036   $43.10   $43.10   $43.10  
  Purchase #4 $50.93   5.495%   $53.7286   $53.73   $53.75   $53.70  
  Purchase #5 $215.94   5.371%   $227.5381   $227.54   $227.55   $227.50  
  Purchase #6 $53.47   11.309%   $59.5169   $59.52   $59.50   $59.50  
  Purchase #7 $216.77   9.547%   $237.465   $237.47   $237.45   $237.50  
  7 purchase totals = $705.26       $755.9747   $755.98   $755.95   $756.00