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 $44.26   4.492%   $46.2482   $46.25   $46.25   $46.20  
  Purchase #2 $201.54   12.108%   $225.9425   $225.94   $225.95   $225.90  
  Purchase #3 $211.67   10.820%   $234.5727   $234.57   $234.55   $234.60  
  Purchase #4 $174.35   11.250%   $193.9644   $193.96   $193.95   $194.00  
  Purchase #5 $174.86   9.485%   $191.4455   $191.45   $191.45   $191.40  
  Purchase #6 $247.93   7.436%   $266.3661   $266.37   $266.35   $266.40  
  Purchase #7 $83.28   10.722%   $92.2093   $92.21   $92.20   $92.20  
  7 purchase totals = $1,137.89       $1,250.7487   $1,250.75   $1,250.70   $1,250.70