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	$219.78	12.736%	$247.7712	$247.77	$247.75	$247.80
Purchase #2	$57.61	8.341%	$62.4153	$62.42	$62.40	$62.40
Purchase #3	$144.79	11.502%	$161.4437	$161.44	$161.45	$161.40
Purchase #4	$59.57	13.397%	$67.5506	$67.55	$67.55	$67.60
Purchase #5	$190.87	10.158%	$210.2586	$210.26	$210.25	$210.30
Purchase #6	$172.82	10.615%	$191.1648	$191.16	$191.15	$191.20
Purchase #7	$171.75	8.825%	$186.9069	$186.91	$186.90	$186.90
7 purchase totals =	$1,017.19		$1,127.5111	$1,127.51	$1,127.45	$1,127.60