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 $191.79   5.317%   $201.9875   $201.99   $202.00   $202.00  
  Purchase #2 $162.34   3.121%   $167.4066   $167.41   $167.40   $167.40  
  Purchase #3 $21.63   11.348%   $24.0846   $24.08   $24.10   $24.10  
  Purchase #4 $44.50   5.395%   $46.9008   $46.90   $46.90   $46.90  
  Purchase #5 $21.51   8.484%   $23.3349   $23.33   $23.35   $23.30  
  Purchase #6 $106.79   3.697%   $110.738   $110.74   $110.75   $110.70  
  Purchase #7 $166.32   11.817%   $185.974   $185.97   $185.95   $186.00  
  7 purchase totals = $714.88       $760.4264   $760.42   $760.45   $760.40