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 $60.95   11.453%   $67.9306   $67.93   $67.95   $67.90  
  Purchase #2 $32.78   13.794%   $37.3017   $37.30   $37.30   $37.30  
  Purchase #3 $246.44   12.536%   $277.3337   $277.33   $277.35   $277.30  
  Purchase #4 $153.62   8.618%   $166.859   $166.86   $166.85   $166.90  
  Purchase #5 $244.93   7.393%   $263.0377   $263.04   $263.05   $263.00  
  Purchase #6 $220.75   6.573%   $235.2599   $235.26   $235.25   $235.30  
  Purchase #7 $142.38   5.299%   $149.9247   $149.92   $149.90   $149.90  
  7 purchase totals = $1,101.85       $1,197.6473   $1,197.64   $1,197.65   $1,197.60