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 $69.93   4.195%   $72.8636   $72.86   $72.85   $72.90  
  Purchase #2 $211.73   13.451%   $240.2098   $240.21   $240.20   $240.20  
  Purchase #3 $56.47   12.554%   $63.5592   $63.56   $63.55   $63.60  
  Purchase #4 $119.72   3.163%   $123.5067   $123.51   $123.50   $123.50  
  Purchase #5 $120.47   10.806%   $133.488   $133.49   $133.50   $133.50  
  Purchase #6 $233.36   4.503%   $243.8682   $243.87   $243.85   $243.90  
  Purchase #7 $147.64   3.767%   $153.2016   $153.20   $153.20   $153.20  
  7 purchase totals = $959.32       $1,030.6971   $1,030.70   $1,030.65   $1,030.80