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	$116.27	13.297%	$131.7304	$131.73	$131.75	$131.70
Purchase #2	$65.84	8.692%	$71.5628	$71.56	$71.55	$71.60
Purchase #3	$128.70	13.132%	$145.6009	$145.60	$145.60	$145.60
Purchase #4	$159.50	8.241%	$172.6444	$172.64	$172.65	$172.60
Purchase #5	$97.51	11.281%	$108.5101	$108.51	$108.50	$108.50
Purchase #6	$85.88	6.116%	$91.1324	$91.13	$91.15	$91.10
Purchase #7	$58.61	6.531%	$62.4378	$62.44	$62.45	$62.40
7 purchase totals =	$712.31		$783.6188	$783.61	$783.65	$783.50