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 $49.94   8.159%   $54.0146   $54.01   $54.00   $54.00  
  Purchase #2 $214.74   11.858%   $240.2039   $240.20   $240.20   $240.20  
  Purchase #3 $203.71   5.837%   $215.6006   $215.60   $215.60   $215.60  
  Purchase #4 $43.86   11.701%   $48.9921   $48.99   $49.00   $49.00  
  Purchase #5 $51.94   6.321%   $55.2231   $55.22   $55.20   $55.20  
  Purchase #6 $220.49   10.146%   $242.8609   $242.86   $242.85   $242.90  
  Purchase #7 $236.89   7.463%   $254.5691   $254.57   $254.55   $254.60  
  7 purchase totals = $1,021.57       $1,111.4643   $1,111.45   $1,111.40   $1,111.50