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	$224.65	11.493%	$250.469	$250.47	$250.45	$250.50
Purchase #2	$56.85	6.172%	$60.3588	$60.36	$60.35	$60.40
Purchase #3	$194.94	7.752%	$210.0517	$210.05	$210.05	$210.10
Purchase #4	$94.66	5.525%	$99.89	$99.89	$99.90	$99.90
Purchase #5	$173.95	12.510%	$195.7111	$195.71	$195.70	$195.70
Purchase #6	$226.27	11.178%	$251.5625	$251.56	$251.55	$251.60
Purchase #7	$78.96	9.114%	$86.1564	$86.16	$86.15	$86.20
7 purchase totals =	$1,050.28		$1,154.1995	$1,154.20	$1,154.15	$1,154.40