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 $86.91   13.766%   $98.874   $98.87   $98.85   $98.90  
  Purchase #2 $185.29   12.335%   $208.1455   $208.15   $208.15   $208.10  
  Purchase #3 $73.28   12.157%   $82.1886   $82.19   $82.20   $82.20  
  Purchase #4 $155.47   7.630%   $167.3324   $167.33   $167.35   $167.30  
  Purchase #5 $225.73   8.389%   $244.6665   $244.67   $244.65   $244.70  
  Purchase #6 $179.95   13.559%   $204.3494   $204.35   $204.35   $204.30  
  Purchase #7 $175.80   6.871%   $187.8792   $187.88   $187.90   $187.90  
  7 purchase totals = $1,082.43       $1,193.4356   $1,193.44   $1,193.45   $1,193.40