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 $48.68   7.532%   $52.3466   $52.35   $52.35   $52.30  
  Purchase #2 $175.33   10.625%   $193.9588   $193.96   $193.95   $194.00  
  Purchase #3 $75.35   4.207%   $78.52   $78.52   $78.50   $78.50  
  Purchase #4 $101.75   5.715%   $107.565   $107.57   $107.55   $107.60  
  Purchase #5 $247.60   10.582%   $273.801   $273.80   $273.80   $273.80  
  Purchase #6 $222.27   12.401%   $249.8337   $249.83   $249.85   $249.80  
  Purchase #7 $15.53   12.687%   $17.5003   $17.50   $17.50   $17.50  
  7 purchase totals = $886.51       $973.5254   $973.53   $973.50   $973.50