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 $189.49   6.126%   $201.0982   $201.10   $201.10   $201.10  
  Purchase #2 $117.93   11.251%   $131.1983   $131.20   $131.20   $131.20  
  Purchase #3 $218.81   6.461%   $232.9473   $232.95   $232.95   $232.90  
  Purchase #4 $41.63   6.579%   $44.3688   $44.37   $44.35   $44.40  
  Purchase #5 $159.35   8.749%   $173.2915   $173.29   $173.30   $173.30  
  Purchase #6 $148.28   13.176%   $167.8174   $167.82   $167.80   $167.80  
  Purchase #7 $208.57   7.697%   $224.6236   $224.62   $224.60   $224.60  
  7 purchase totals = $1,084.06       $1,175.3451   $1,175.35   $1,175.30   $1,175.30