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 $89.53   6.390%   $95.251   $95.25   $95.25   $95.30  
  Purchase #2 $240.48   8.282%   $260.3966   $260.40   $260.40   $260.40  
  Purchase #3 $223.98   4.290%   $233.5887   $233.59   $233.60   $233.60  
  Purchase #4 $98.97   8.177%   $107.0628   $107.06   $107.05   $107.10  
  Purchase #5 $23.57   8.246%   $25.5136   $25.51   $25.50   $25.50  
  Purchase #6 $44.49   3.230%   $45.927   $45.93   $45.95   $45.90  
  Purchase #7 $95.85   11.873%   $107.2303   $107.23   $107.25   $107.20  
  7 purchase totals = $816.87       $874.9700   $874.97   $875.00   $875.00