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 $84.70   12.660%   $95.423   $95.42   $95.40   $95.40  
  Purchase #2 $169.64   13.496%   $192.5346   $192.53   $192.55   $192.50  
  Purchase #3 $209.43   11.770%   $234.0799   $234.08   $234.10   $234.10  
  Purchase #4 $238.93   6.144%   $253.6099   $253.61   $253.60   $253.60  
  Purchase #5 $58.62   4.614%   $61.3247   $61.32   $61.30   $61.30  
  Purchase #6 $123.86   8.707%   $134.6445   $134.64   $134.65   $134.60  
  Purchase #7 $176.87   13.846%   $201.3594   $201.36   $201.35   $201.40  
  7 purchase totals = $1,062.05       $1,172.9760   $1,172.96   $1,172.95   $1,172.90