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 $42.83   9.390%   $46.8517   $46.85   $46.85   $46.90  
  Purchase #2 $98.38   5.462%   $103.7535   $103.75   $103.75   $103.80  
  Purchase #3 $30.44   13.846%   $34.6547   $34.65   $34.65   $34.70  
  Purchase #4 $55.92   10.816%   $61.9683   $61.97   $61.95   $62.00  
  Purchase #5 $230.98   9.642%   $253.2511   $253.25   $253.25   $253.30  
  Purchase #6 $165.62   11.624%   $184.8717   $184.87   $184.85   $184.90  
  Purchase #7 $71.30   10.831%   $79.0225   $79.02   $79.00   $79.00  
  7 purchase totals = $695.47       $764.3735   $764.36   $764.30   $764.60