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	$217.71	7.230%	$233.4504	$233.45	$233.45	$233.50
Purchase #2	$87.67	13.368%	$99.3897	$99.39	$99.40	$99.40
Purchase #3	$142.94	11.683%	$159.6397	$159.64	$159.65	$159.60
Purchase #4	$244.98	9.634%	$268.5814	$268.58	$268.60	$268.60
Purchase #5	$59.56	4.380%	$62.1687	$62.17	$62.15	$62.20
Purchase #6	$152.60	4.851%	$160.0026	$160.00	$160.00	$160.00
Purchase #7	$82.39	6.445%	$87.7	$87.70	$87.70	$87.70
7 purchase totals =	$987.85		$1,070.9325	$1,070.93	$1,070.95	$1,071.00