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	$156.55	11.187%	$174.0632	$174.06	$174.05	$174.10
Purchase #2	$160.49	11.360%	$178.7217	$178.72	$178.70	$178.70
Purchase #3	$54.84	4.324%	$57.2113	$57.21	$57.20	$57.20
Purchase #4	$50.72	10.388%	$55.9888	$55.99	$56.00	$56.00
Purchase #5	$146.76	12.615%	$165.2738	$165.27	$165.25	$165.30
Purchase #6	$72.42	13.847%	$82.448	$82.45	$82.45	$82.40
Purchase #7	$60.79	10.582%	$67.2228	$67.22	$67.20	$67.20
7 purchase totals =	$702.57		$780.9296	$780.92	$780.85	$780.90