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	$108.27	7.675%	$116.5797	$116.58	$116.60	$116.60
Purchase #2	$51.81	9.331%	$56.6444	$56.64	$56.65	$56.60
Purchase #3	$162.47	7.385%	$174.4684	$174.47	$174.45	$174.50
Purchase #4	$56.43	7.383%	$60.5962	$60.60	$60.60	$60.60
Purchase #5	$79.76	11.729%	$89.1151	$89.12	$89.10	$89.10
Purchase #6	$106.48	7.513%	$114.4798	$114.48	$114.50	$114.50
Purchase #7	$62.97	13.873%	$71.7058	$71.71	$71.70	$71.70
7 purchase totals =	$628.19		$683.5894	$683.60	$683.60	$683.60