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 $92.73   3.534%   $96.0071   $96.01   $96.00   $96.00  
  Purchase #2 $202.75   7.196%   $217.3399   $217.34   $217.35   $217.30  
  Purchase #3 $60.49   4.595%   $63.2695   $63.27   $63.25   $63.30  
  Purchase #4 $249.26   13.762%   $283.5632   $283.56   $283.55   $283.60  
  Purchase #5 $23.53   3.344%   $24.3168   $24.32   $24.30   $24.30  
  Purchase #6 $183.38   6.835%   $195.914   $195.91   $195.90   $195.90  
  Purchase #7 $244.37   12.768%   $275.5712   $275.57   $275.55   $275.60  
  7 purchase totals = $1,056.51       $1,155.9817   $1,155.98   $1,155.90   $1,156.00