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 $92.59   3.174%   $95.5288   $95.53   $95.55   $95.50  
  Purchase #2 $18.73   6.433%   $19.9349   $19.93   $19.95   $19.90  
  Purchase #3 $160.52   9.671%   $176.0439   $176.04   $176.05   $176.00  
  Purchase #4 $92.86   3.462%   $96.0748   $96.07   $96.05   $96.10  
  Purchase #5 $232.62   5.356%   $245.0791   $245.08   $245.10   $245.10  
  Purchase #6 $21.78   10.216%   $24.005   $24.01   $24.00   $24.00  
  Purchase #7 $70.39   3.630%   $72.9452   $72.95   $72.95   $72.90  
  7 purchase totals = $689.49       $729.6117   $729.61   $729.65   $729.50