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 $211.93   11.205%   $235.6768   $235.68   $235.70   $235.70  
  Purchase #2 $230.74   10.774%   $255.5999   $255.60   $255.60   $255.60  
  Purchase #3 $115.92   8.144%   $125.3605   $125.36   $125.35   $125.40  
  Purchase #4 $45.71   9.671%   $50.1306   $50.13   $50.15   $50.10  
  Purchase #5 $141.44   5.698%   $149.4993   $149.50   $149.50   $149.50  
  Purchase #6 $45.47   9.502%   $49.7906   $49.79   $49.80   $49.80  
  Purchase #7 $172.78   4.621%   $180.7642   $180.76   $180.75   $180.80  
  7 purchase totals = $963.99       $1,046.8219   $1,046.82   $1,046.85   $1,046.90