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 $22.49   3.481%   $23.2729   $23.27   $23.25   $23.30  
  Purchase #2 $216.84   11.274%   $241.2865   $241.29   $241.30   $241.30  
  Purchase #3 $224.75   5.828%   $237.8484   $237.85   $237.85   $237.80  
  Purchase #4 $160.45   5.714%   $169.6181   $169.62   $169.60   $169.60  
  Purchase #5 $35.63   6.474%   $37.9367   $37.94   $37.95   $37.90  
  Purchase #6 $195.78   4.106%   $203.8187   $203.82   $203.80   $203.80  
  Purchase #7 $211.34   3.278%   $218.2677   $218.27   $218.25   $218.30  
  7 purchase totals = $1,067.28       $1,132.0490   $1,132.06   $1,132.00   $1,132.00