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	$237.29	5.845%	$251.1596	$251.16	$251.15	$251.20
Purchase #2	$36.47	8.748%	$39.6604	$39.66	$39.65	$39.70
Purchase #3	$16.43	11.464%	$18.3135	$18.31	$18.30	$18.30
Purchase #4	$112.39	9.696%	$123.2873	$123.29	$123.30	$123.30
Purchase #5	$174.75	9.567%	$191.4683	$191.47	$191.45	$191.50
Purchase #6	$247.92	8.458%	$268.8891	$268.89	$268.90	$268.90
Purchase #7	$161.92	6.700%	$172.7686	$172.77	$172.75	$172.80
7 purchase totals =	$987.17		$1,065.5468	$1,065.55	$1,065.50	$1,065.70