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	$109.51	6.169%	$116.2657	$116.27	$116.25	$116.30
Purchase #2	$71.97	12.143%	$80.7093	$80.71	$80.70	$80.70
Purchase #3	$158.89	8.456%	$172.3257	$172.33	$172.35	$172.30
Purchase #4	$71.86	6.138%	$76.2708	$76.27	$76.25	$76.30
Purchase #5	$197.90	3.343%	$204.5158	$204.52	$204.50	$204.50
Purchase #6	$175.86	3.412%	$181.8603	$181.86	$181.85	$181.90
Purchase #7	$211.63	12.263%	$237.5822	$237.58	$237.60	$237.60
7 purchase totals =	$997.62		$1,069.5298	$1,069.54	$1,069.50	$1,069.60