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 $169.29   13.800%   $192.652   $192.65   $192.65   $192.70  
  Purchase #2 $187.47   5.216%   $197.2484   $197.25   $197.25   $197.20  
  Purchase #3 $23.28   7.288%   $24.9766   $24.98   $25.00   $25.00  
  Purchase #4 $217.64   5.519%   $229.6516   $229.65   $229.65   $229.70  
  Purchase #5 $180.35   7.123%   $193.1963   $193.20   $193.20   $193.20  
  Purchase #6 $130.63   12.516%   $146.9797   $146.98   $147.00   $147.00  
  Purchase #7 $23.61   6.561%   $25.1591   $25.16   $25.15   $25.20  
  7 purchase totals = $932.27       $1,009.8637   $1,009.87   $1,009.90   $1,010.00