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 $194.90   3.110%   $200.9614   $200.96   $200.95   $201.00  
  Purchase #2 $95.68   9.336%   $104.6127   $104.61   $104.60   $104.60  
  Purchase #3 $170.43   5.247%   $179.3725   $179.37   $179.35   $179.40  
  Purchase #4 $115.80   3.378%   $119.7117   $119.71   $119.70   $119.70  
  Purchase #5 $178.84   6.138%   $189.8172   $189.82   $189.80   $189.80  
  Purchase #6 $61.96   4.612%   $64.8176   $64.82   $64.80   $64.80  
  Purchase #7 $230.83   11.452%   $257.2647   $257.26   $257.25   $257.30  
  7 purchase totals = $1,048.44       $1,116.5578   $1,116.55   $1,116.45   $1,116.60