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	$127.41	3.319%	$131.6387	$131.64	$131.65	$131.60
Purchase #2	$105.62	7.263%	$113.2912	$113.29	$113.30	$113.30
Purchase #3	$212.53	11.795%	$237.5979	$237.60	$237.60	$237.60
Purchase #4	$62.84	13.472%	$71.3058	$71.31	$71.30	$71.30
Purchase #5	$18.45	13.233%	$20.8915	$20.89	$20.90	$20.90
Purchase #6	$109.56	7.258%	$117.5119	$117.51	$117.50	$117.50
Purchase #7	$58.95	6.177%	$62.5913	$62.59	$62.60	$62.60
7 purchase totals =	$695.36		$754.8283	$754.83	$754.85	$754.80