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	$165.95	9.502%	$181.7186	$181.72	$181.70	$181.70
Purchase #2	$242.31	3.333%	$250.3862	$250.39	$250.40	$250.40
Purchase #3	$215.70	10.157%	$237.6086	$237.61	$237.60	$237.60
Purchase #4	$134.74	7.827%	$145.2861	$145.29	$145.30	$145.30
Purchase #5	$84.34	13.728%	$95.9182	$95.92	$95.90	$95.90
Purchase #6	$104.41	13.290%	$118.2861	$118.29	$118.30	$118.30
Purchase #7	$158.67	5.720%	$167.7459	$167.75	$167.75	$167.70
7 purchase totals =	$1,106.12		$1,196.9497	$1,196.97	$1,196.95	$1,196.90