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	$213.55	9.400%	$233.6237	$233.62	$233.60	$233.60
Purchase #2	$226.86	12.814%	$255.9298	$255.93	$255.95	$255.90
Purchase #3	$197.40	10.585%	$218.2948	$218.29	$218.30	$218.30
Purchase #4	$145.50	4.518%	$152.0737	$152.07	$152.05	$152.10
Purchase #5	$105.95	11.316%	$117.9393	$117.94	$117.95	$117.90
Purchase #6	$66.27	12.413%	$74.4961	$74.50	$74.50	$74.50
Purchase #7	$12.84	3.352%	$13.2704	$13.27	$13.25	$13.30
7 purchase totals =	$968.37		$1,065.6278	$1,065.62	$1,065.60	$1,065.60