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 $147.96   10.476%   $163.4603   $163.46   $163.45   $163.50  
  Purchase #2 $147.94   9.634%   $162.1925   $162.19   $162.20   $162.20  
  Purchase #3 $62.85   5.754%   $66.4664   $66.47   $66.45   $66.50  
  Purchase #4 $168.55   13.852%   $191.8975   $191.90   $191.90   $191.90  
  Purchase #5 $134.28   4.409%   $140.2004   $140.20   $140.20   $140.20  
  Purchase #6 $229.79   10.754%   $254.5016   $254.50   $254.50   $254.50  
  Purchase #7 $183.61   7.408%   $197.2118   $197.21   $197.20   $197.20  
  7 purchase totals = $1,074.98       $1,175.9305   $1,175.93   $1,175.90   $1,176.00