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 $193.48   7.823%   $208.6159   $208.62   $208.60   $208.60  
  Purchase #2 $49.95   9.405%   $54.6478   $54.65   $54.65   $54.60  
  Purchase #3 $120.76   11.634%   $134.8092   $134.81   $134.80   $134.80  
  Purchase #4 $59.48   12.496%   $66.9126   $66.91   $66.90   $66.90  
  Purchase #5 $223.87   7.430%   $240.5035   $240.50   $240.50   $240.50  
  Purchase #6 $225.89   10.769%   $250.2161   $250.22   $250.20   $250.20  
  Purchase #7 $148.29   4.406%   $154.8237   $154.82   $154.80   $154.80  
  7 purchase totals = $1,021.72       $1,110.5288   $1,110.53   $1,110.45   $1,110.40