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 $245.90   7.586%   $264.554   $264.55   $264.55   $264.60  
  Purchase #2 $221.53   5.152%   $232.9432   $232.94   $232.95   $232.90  
  Purchase #3 $217.61   3.478%   $225.1785   $225.18   $225.20   $225.20  
  Purchase #4 $154.51   9.197%   $168.7203   $168.72   $168.70   $168.70  
  Purchase #5 $21.81   11.580%   $24.3356   $24.34   $24.35   $24.30  
  Purchase #6 $96.70   6.566%   $103.0493   $103.05   $103.05   $103.00  
  Purchase #7 $84.52   3.793%   $87.7258   $87.73   $87.75   $87.70  
  7 purchase totals = $1,042.58       $1,106.5067   $1,106.51   $1,106.55   $1,106.40