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	$68.95	12.478%	$77.5536	$77.55	$77.55	$77.60
Purchase #2	$129.92	12.190%	$145.7572	$145.76	$145.75	$145.80
Purchase #3	$184.57	6.515%	$196.5947	$196.59	$196.60	$196.60
Purchase #4	$153.31	9.389%	$167.7043	$167.70	$167.70	$167.70
Purchase #5	$202.92	10.654%	$224.5391	$224.54	$224.55	$224.50
Purchase #6	$63.71	4.613%	$66.6489	$66.65	$66.65	$66.60
Purchase #7	$153.63	12.430%	$172.7262	$172.73	$172.75	$172.70
7 purchase totals =	$957.01		$1,051.5240	$1,051.52	$1,051.55	$1,051.50