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 $175.42   11.135%   $194.953   $194.95   $194.95   $195.00  
  Purchase #2 $72.84   12.838%   $82.1912   $82.19   $82.20   $82.20  
  Purchase #3 $156.51   5.576%   $165.237   $165.24   $165.25   $165.20  
  Purchase #4 $93.82   4.247%   $97.8045   $97.80   $97.80   $97.80  
  Purchase #5 $106.36   6.727%   $113.5148   $113.51   $113.50   $113.50  
  Purchase #6 $224.87   12.113%   $252.1085   $252.11   $252.10   $252.10  
  Purchase #7 $8.31   11.614%   $9.2751   $9.28   $9.30   $9.30  
  7 purchase totals = $838.13       $915.0841   $915.08   $915.10   $915.10