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	$191.91	10.383%	$211.836	$211.84	$211.85	$211.80
Purchase #2	$210.92	9.346%	$230.6326	$230.63	$230.65	$230.60
Purchase #3	$152.77	3.551%	$158.1949	$158.19	$158.20	$158.20
Purchase #4	$222.85	4.602%	$233.1056	$233.11	$233.10	$233.10
Purchase #5	$128.63	11.125%	$142.9401	$142.94	$142.95	$142.90
Purchase #6	$178.89	12.108%	$200.55	$200.55	$200.55	$200.60
Purchase #7	$235.57	12.253%	$264.4344	$264.43	$264.45	$264.40
7 purchase totals =	$1,321.54		$1,441.6936	$1,441.69	$1,441.75	$1,441.60