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 $71.25   6.705%   $76.0273   $76.03   $76.05   $76.00  
  Purchase #2 $31.58   4.568%   $33.0226   $33.02   $33.00   $33.00  
  Purchase #3 $124.59   8.286%   $134.9135   $134.91   $134.90   $134.90  
  Purchase #4 $132.32   11.243%   $147.1967   $147.20   $147.20   $147.20  
  Purchase #5 $182.40   6.636%   $194.5041   $194.50   $194.50   $194.50  
  Purchase #6 $183.69   5.766%   $194.2816   $194.28   $194.30   $194.30  
  Purchase #7 $35.65   13.133%   $40.3319   $40.33   $40.35   $40.30  
  7 purchase totals = $761.48       $820.2777   $820.27   $820.30   $820.20