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 $58.49   4.355%   $61.0372   $61.04   $61.05   $61.00  
  Purchase #2 $61.62   3.206%   $63.5955   $63.60   $63.60   $63.60  
  Purchase #3 $221.25   5.637%   $233.7219   $233.72   $233.70   $233.70  
  Purchase #4 $178.88   6.760%   $190.9723   $190.97   $190.95   $191.00  
  Purchase #5 $184.44   5.332%   $194.2743   $194.27   $194.25   $194.30  
  Purchase #6 $79.92   10.561%   $88.3604   $88.36   $88.35   $88.40  
  Purchase #7 $237.69   10.372%   $262.3432   $262.34   $262.35   $262.30  
  7 purchase totals = $1,022.29       $1,094.3048   $1,094.30   $1,094.25   $1,094.30