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 $89.41   6.242%   $94.991   $94.99   $95.00   $95.00  
  Purchase #2 $192.53   13.158%   $217.8631   $217.86   $217.85   $217.90  
  Purchase #3 $79.94   9.722%   $87.7118   $87.71   $87.70   $87.70  
  Purchase #4 $216.70   11.720%   $242.0972   $242.10   $242.10   $242.10  
  Purchase #5 $226.43   8.792%   $246.3377   $246.34   $246.35   $246.30  
  Purchase #6 $23.57   9.496%   $25.8082   $25.81   $25.80   $25.80  
  Purchase #7 $107.64   11.230%   $119.728   $119.73   $119.75   $119.70  
  7 purchase totals = $936.22       $1,034.5370   $1,034.54   $1,034.55   $1,034.50