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 $98.49   8.607%   $106.967   $106.97   $106.95   $107.00  
  Purchase #2 $54.33   9.519%   $59.5017   $59.50   $59.50   $59.50  
  Purchase #3 $168.79   4.771%   $176.843   $176.84   $176.85   $176.80  
  Purchase #4 $73.93   7.396%   $79.3979   $79.40   $79.40   $79.40  
  Purchase #5 $160.73   8.821%   $174.908   $174.91   $174.90   $174.90  
  Purchase #6 $120.29   11.721%   $134.3892   $134.39   $134.40   $134.40  
  Purchase #7 $51.53   6.319%   $54.7862   $54.79   $54.80   $54.80  
  7 purchase totals = $728.09       $786.7930   $786.80   $786.80   $786.80