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 $83.46   13.785%   $94.965   $94.97   $94.95   $95.00  
  Purchase #2 $229.65   13.133%   $259.8099   $259.81   $259.80   $259.80  
  Purchase #3 $56.44   11.810%   $63.1056   $63.11   $63.10   $63.10  
  Purchase #4 $135.25   13.839%   $153.9672   $153.97   $153.95   $154.00  
  Purchase #5 $239.50   5.411%   $252.4593   $252.46   $252.45   $252.50  
  Purchase #6 $129.91   13.633%   $147.6206   $147.62   $147.60   $147.60  
  Purchase #7 $199.36   9.780%   $218.8574   $218.86   $218.85   $218.90  
  7 purchase totals = $1,073.57       $1,190.7850   $1,190.80   $1,190.70   $1,190.90