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	$48.41	13.718%	$55.0509	$55.05	$55.05	$55.10
Purchase #2	$93.63	13.845%	$106.5931	$106.59	$106.60	$106.60
Purchase #3	$103.99	13.364%	$117.8872	$117.89	$117.90	$117.90
Purchase #4	$17.95	5.251%	$18.8926	$18.89	$18.90	$18.90
Purchase #5	$80.29	11.787%	$89.7538	$89.75	$89.75	$89.80
Purchase #6	$240.64	4.181%	$250.7012	$250.70	$250.70	$250.70
Purchase #7	$90.71	4.191%	$94.5117	$94.51	$94.50	$94.50
7 purchase totals =	$675.62		$733.3905	$733.38	$733.40	$733.50