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 $208.49   13.107%   $235.8168   $235.82   $235.80   $235.80  
  Purchase #2 $206.90   4.299%   $215.7946   $215.79   $215.80   $215.80  
  Purchase #3 $159.87   10.240%   $176.2407   $176.24   $176.25   $176.20  
  Purchase #4 $11.91   5.580%   $12.5746   $12.57   $12.55   $12.60  
  Purchase #5 $91.76   6.556%   $97.7758   $97.78   $97.80   $97.80  
  Purchase #6 $137.53   13.741%   $156.428   $156.43   $156.45   $156.40  
  Purchase #7 $121.57   7.611%   $130.8227   $130.82   $130.80   $130.80  
  7 purchase totals = $938.03       $1,025.4532   $1,025.45   $1,025.45   $1,025.40