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	$197.64	8.408%	$214.2576	$214.26	$214.25	$214.30
Purchase #2	$166.34	11.442%	$185.3726	$185.37	$185.35	$185.40
Purchase #3	$244.30	12.861%	$275.7194	$275.72	$275.70	$275.70
Purchase #4	$202.55	10.274%	$223.36	$223.36	$223.35	$223.40
Purchase #5	$245.29	8.360%	$265.7962	$265.80	$265.80	$265.80
Purchase #6	$127.28	13.848%	$144.9057	$144.91	$144.90	$144.90
Purchase #7	$54.87	13.274%	$62.1534	$62.15	$62.15	$62.20
7 purchase totals =	$1,238.27		$1,371.5649	$1,371.57	$1,371.50	$1,371.70