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 $195.76   11.741%   $218.7442   $218.74   $218.75   $218.70  
  Purchase #2 $56.82   10.606%   $62.8463   $62.85   $62.85   $62.80  
  Purchase #3 $160.25   11.288%   $178.339   $178.34   $178.35   $178.30  
  Purchase #4 $39.82   5.176%   $41.8811   $41.88   $41.90   $41.90  
  Purchase #5 $192.91   9.674%   $211.5721   $211.57   $211.55   $211.60  
  Purchase #6 $182.98   5.629%   $193.2799   $193.28   $193.30   $193.30  
  Purchase #7 $195.53   10.713%   $216.4771   $216.48   $216.50   $216.50  
  7 purchase totals = $1,024.07       $1,123.1397   $1,123.14   $1,123.20   $1,123.10