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	$222.29	5.308%	$234.0892	$234.09	$234.10	$234.10
Purchase #2	$101.43	9.761%	$111.3306	$111.33	$111.35	$111.30
Purchase #3	$189.84	5.428%	$200.1445	$200.14	$200.15	$200.10
Purchase #4	$53.67	6.575%	$57.1988	$57.20	$57.20	$57.20
Purchase #5	$131.73	11.179%	$146.4561	$146.46	$146.45	$146.50
Purchase #6	$148.40	10.179%	$163.5056	$163.51	$163.50	$163.50
Purchase #7	$62.93	5.695%	$66.5139	$66.51	$66.50	$66.50
7 purchase totals =	$910.29		$979.2387	$979.24	$979.25	$979.20