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 $73.48   3.254%   $75.871   $75.87   $75.85   $75.90  
  Purchase #2 $244.65   7.803%   $263.74   $263.74   $263.75   $263.70  
  Purchase #3 $66.62   11.829%   $74.5005   $74.50   $74.50   $74.50  
  Purchase #4 $248.73   7.160%   $266.5391   $266.54   $266.55   $266.50  
  Purchase #5 $90.25   8.157%   $97.6117   $97.61   $97.60   $97.60  
  Purchase #6 $145.51   8.572%   $157.9831   $157.98   $158.00   $158.00  
  Purchase #7 $80.46   7.395%   $86.41   $86.41   $86.40   $86.40  
  7 purchase totals = $949.70       $1,022.6554   $1,022.65   $1,022.65   $1,022.60