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 $59.33   6.507%   $63.1906   $63.19   $63.20   $63.20  
  Purchase #2 $98.59   4.428%   $102.9556   $102.96   $102.95   $103.00  
  Purchase #3 $208.45   5.721%   $220.3754   $220.38   $220.40   $220.40  
  Purchase #4 $31.67   5.108%   $33.2877   $33.29   $33.30   $33.30  
  Purchase #5 $152.33   7.187%   $163.278   $163.28   $163.30   $163.30  
  Purchase #6 $245.75   7.209%   $263.4661   $263.47   $263.45   $263.50  
  Purchase #7 $227.39   5.433%   $239.7441   $239.74   $239.75   $239.70  
  7 purchase totals = $1,023.51       $1,086.2975   $1,086.31   $1,086.35   $1,086.40