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 $71.84   5.512%   $75.7998   $75.80   $75.80   $75.80  
  Purchase #2 $174.52   6.809%   $186.4031   $186.40   $186.40   $186.40  
  Purchase #3 $7.77   3.255%   $8.0229   $8.02   $8.00   $8.00  
  Purchase #4 $54.74   11.258%   $60.9026   $60.90   $60.90   $60.90  
  Purchase #5 $96.92   4.181%   $100.9722   $100.97   $100.95   $101.00  
  Purchase #6 $113.65   11.816%   $127.0789   $127.08   $127.10   $127.10  
  Purchase #7 $196.64   12.857%   $221.922   $221.92   $221.90   $221.90  
  7 purchase totals = $716.08       $781.1015   $781.09   $781.05   $781.10