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	$127.66	11.636%	$142.5145	$142.51	$142.50	$142.50
Purchase #2	$22.45	13.251%	$25.4248	$25.42	$25.40	$25.40
Purchase #3	$70.89	6.340%	$75.3844	$75.38	$75.40	$75.40
Purchase #4	$88.56	4.223%	$92.2999	$92.30	$92.30	$92.30
Purchase #5	$32.62	11.663%	$36.4245	$36.42	$36.40	$36.40
Purchase #6	$109.81	6.375%	$116.8104	$116.81	$116.80	$116.80
Purchase #7	$134.59	5.251%	$141.6573	$141.66	$141.65	$141.70
7 purchase totals =	$586.58		$630.5158	$630.50	$630.45	$630.50