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	$101.51	12.834%	$114.5378	$114.54	$114.55	$114.50
Purchase #2	$59.44	10.869%	$65.9005	$65.90	$65.90	$65.90
Purchase #3	$245.39	11.640%	$273.9534	$273.95	$273.95	$274.00
Purchase #4	$16.76	9.126%	$18.2895	$18.29	$18.30	$18.30
Purchase #5	$140.89	7.438%	$151.3694	$151.37	$151.35	$151.40
Purchase #6	$196.35	11.367%	$218.6691	$218.67	$218.65	$218.70
Purchase #7	$240.78	3.151%	$248.367	$248.37	$248.35	$248.40
7 purchase totals =	$1,001.12		$1,091.0867	$1,091.09	$1,091.05	$1,091.20