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	$176.29	6.368%	$187.5161	$187.52	$187.50	$187.50
Purchase #2	$60.41	3.585%	$62.5757	$62.58	$62.60	$62.60
Purchase #3	$80.96	10.760%	$89.6713	$89.67	$89.65	$89.70
Purchase #4	$198.92	9.501%	$217.8194	$217.82	$217.80	$217.80
Purchase #5	$184.69	8.534%	$200.4514	$200.45	$200.45	$200.50
Purchase #6	$238.56	3.693%	$247.37	$247.37	$247.35	$247.40
Purchase #7	$202.48	12.722%	$228.2395	$228.24	$228.25	$228.20
7 purchase totals =	$1,142.31		$1,233.6434	$1,233.65	$1,233.60	$1,233.70