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	$49.74	11.164%	$55.293	$55.29	$55.30	$55.30
Purchase #2	$224.26	13.289%	$254.0619	$254.06	$254.05	$254.10
Purchase #3	$80.83	12.211%	$90.7002	$90.70	$90.70	$90.70
Purchase #4	$249.58	3.162%	$257.4717	$257.47	$257.45	$257.50
Purchase #5	$187.47	3.141%	$193.3584	$193.36	$193.35	$193.40
Purchase #6	$82.47	8.586%	$89.5509	$89.55	$89.55	$89.60
Purchase #7	$83.29	11.498%	$92.8667	$92.87	$92.85	$92.90
7 purchase totals =	$957.64		$1,033.3028	$1,033.30	$1,033.25	$1,033.50