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 $244.29   7.748%   $263.2176   $263.22   $263.20   $263.20  
  Purchase #2 $152.60   11.143%   $169.6042   $169.60   $169.60   $169.60  
  Purchase #3 $119.90   4.261%   $125.0089   $125.01   $125.00   $125.00  
  Purchase #4 $176.88   11.770%   $197.6988   $197.70   $197.70   $197.70  
  Purchase #5 $80.73   13.662%   $91.7593   $91.76   $91.75   $91.80  
  Purchase #6 $74.55   7.674%   $80.271   $80.27   $80.25   $80.30  
  Purchase #7 $116.49   5.456%   $122.8457   $122.85   $122.85   $122.80  
  7 purchase totals = $965.44       $1,050.4055   $1,050.41   $1,050.35   $1,050.40