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 $59.49   4.718%   $62.2967   $62.30   $62.30   $62.30  
  Purchase #2 $95.52   11.208%   $106.2259   $106.23   $106.25   $106.20  
  Purchase #3 $160.96   10.734%   $178.2374   $178.24   $178.25   $178.20  
  Purchase #4 $240.73   8.282%   $260.6673   $260.67   $260.65   $260.70  
  Purchase #5 $35.36   7.264%   $37.9286   $37.93   $37.95   $37.90  
  Purchase #6 $33.88   4.119%   $35.2755   $35.28   $35.30   $35.30  
  Purchase #7 $165.45   8.644%   $179.7515   $179.75   $179.75   $179.80  
  7 purchase totals = $791.39       $860.3829   $860.40   $860.45   $860.40