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	$73.72	12.389%	$82.8532	$82.85	$82.85	$82.90
Purchase #2	$87.76	4.741%	$91.9207	$91.92	$91.90	$91.90
Purchase #3	$138.47	9.479%	$151.5956	$151.60	$151.60	$151.60
Purchase #4	$74.46	11.336%	$82.9008	$82.90	$82.90	$82.90
Purchase #5	$157.52	10.867%	$174.6377	$174.64	$174.65	$174.60
Purchase #6	$216.67	3.120%	$223.4301	$223.43	$223.45	$223.40
Purchase #7	$210.32	5.346%	$221.5637	$221.56	$221.55	$221.60
7 purchase totals =	$958.92		$1,028.9018	$1,028.90	$1,028.90	$1,028.90