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 $89.84   5.738%   $94.995   $95.00   $95.00   $95.00  
  Purchase #2 $49.33   3.609%   $51.1103   $51.11   $51.10   $51.10  
  Purchase #3 $5.88   12.729%   $6.6285   $6.63   $6.65   $6.60  
  Purchase #4 $161.39   5.359%   $170.0389   $170.04   $170.05   $170.00  
  Purchase #5 $160.60   8.519%   $174.2815   $174.28   $174.30   $174.30  
  Purchase #6 $9.50   6.359%   $10.1041   $10.10   $10.10   $10.10  
  Purchase #7 $111.37   6.466%   $118.5712   $118.57   $118.55   $118.60  
  7 purchase totals = $587.91       $625.7295   $625.73   $625.75   $625.70