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 $176.89   10.419%   $195.3202   $195.32   $195.30   $195.30  
  Purchase #2 $176.45   12.103%   $197.8057   $197.81   $197.80   $197.80  
  Purchase #3 $145.98   5.837%   $154.5009   $154.50   $154.50   $154.50  
  Purchase #4 $172.92   12.449%   $194.4468   $194.45   $194.45   $194.40  
  Purchase #5 $38.86   4.849%   $40.7443   $40.74   $40.75   $40.70  
  Purchase #6 $44.88   5.534%   $47.3637   $47.36   $47.35   $47.40  
  Purchase #7 $143.93   6.169%   $152.809   $152.81   $152.80   $152.80  
  7 purchase totals = $899.91       $982.9906   $982.99   $982.95   $982.90