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 $114.40   10.655%   $126.5893   $126.59   $126.60   $126.60  
  Purchase #2 $244.66   6.281%   $260.0271   $260.03   $260.05   $260.00  
  Purchase #3 $237.85   8.553%   $258.1933   $258.19   $258.20   $258.20  
  Purchase #4 $58.82   6.201%   $62.4674   $62.47   $62.45   $62.50  
  Purchase #5 $61.84   11.126%   $68.7203   $68.72   $68.70   $68.70  
  Purchase #6 $99.80   11.331%   $111.1083   $111.11   $111.10   $111.10  
  Purchase #7 $173.66   6.699%   $185.2935   $185.29   $185.30   $185.30  
  7 purchase totals = $991.03       $1,072.3992   $1,072.40   $1,072.40   $1,072.40