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 $94.90   3.588%   $98.305   $98.31   $98.30   $98.30  
  Purchase #2 $147.48   13.591%   $167.524   $167.52   $167.50   $167.50  
  Purchase #3 $58.49   9.778%   $64.2092   $64.21   $64.20   $64.20  
  Purchase #4 $145.78   13.103%   $164.8816   $164.88   $164.90   $164.90  
  Purchase #5 $10.49   5.109%   $11.0259   $11.03   $11.05   $11.00  
  Purchase #6 $22.96   6.260%   $24.3973   $24.40   $24.40   $24.40  
  Purchase #7 $191.28   12.853%   $215.8652   $215.87   $215.85   $215.90  
  7 purchase totals = $671.38       $746.2082   $746.22   $746.20   $746.20