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 $194.62   3.557%   $201.5426   $201.54   $201.55   $201.50  
  Purchase #2 $137.40   5.541%   $145.0133   $145.01   $145.00   $145.00  
  Purchase #3 $166.78   5.562%   $176.0563   $176.06   $176.05   $176.10  
  Purchase #4 $159.63   4.222%   $166.3696   $166.37   $166.35   $166.40  
  Purchase #5 $221.52   10.133%   $243.9666   $243.97   $243.95   $244.00  
  Purchase #6 $162.94   8.848%   $177.3569   $177.36   $177.35   $177.40  
  Purchase #7 $62.35   5.347%   $65.6839   $65.68   $65.70   $65.70  
  7 purchase totals = $1,105.24       $1,175.9892   $1,175.99   $1,175.95   $1,176.10