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 $152.60   10.247%   $168.2369   $168.24   $168.25   $168.20  
  Purchase #2 $60.41   10.646%   $66.8412   $66.84   $66.85   $66.80  
  Purchase #3 $73.84   3.581%   $76.4842   $76.48   $76.50   $76.50  
  Purchase #4 $177.64   8.318%   $192.4161   $192.42   $192.40   $192.40  
  Purchase #5 $235.91   3.464%   $244.0819   $244.08   $244.10   $244.10  
  Purchase #6 $75.98   9.388%   $83.113   $83.11   $83.10   $83.10  
  Purchase #7 $195.88   11.532%   $218.4689   $218.47   $218.45   $218.50  
  7 purchase totals = $972.26       $1,049.6422   $1,049.64   $1,049.65   $1,049.60