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	$122.52	3.787%	$127.1598	$127.16	$127.15	$127.20
Purchase #2	$146.46	5.196%	$154.0701	$154.07	$154.05	$154.10
Purchase #3	$32.35	13.638%	$36.7619	$36.76	$36.75	$36.80
Purchase #4	$51.88	9.364%	$56.738	$56.74	$56.75	$56.70
Purchase #5	$76.93	7.749%	$82.8913	$82.89	$82.90	$82.90
Purchase #6	$99.94	8.621%	$108.5558	$108.56	$108.55	$108.60
Purchase #7	$95.53	5.763%	$101.0354	$101.04	$101.05	$101.00
7 purchase totals =	$625.61		$667.2123	$667.22	$667.20	$667.30