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	$242.53	7.440%	$260.5742	$260.57	$260.55	$260.60
Purchase #2	$231.29	7.404%	$248.4147	$248.41	$248.40	$248.40
Purchase #3	$152.52	8.228%	$165.0693	$165.07	$165.05	$165.10
Purchase #4	$202.33	6.852%	$216.1937	$216.19	$216.20	$216.20
Purchase #5	$244.27	12.767%	$275.456	$275.46	$275.45	$275.50
Purchase #6	$116.43	9.272%	$127.2254	$127.23	$127.25	$127.20
Purchase #7	$99.91	11.470%	$111.3697	$111.37	$111.35	$111.40
7 purchase totals =	$1,289.28		$1,404.3030	$1,404.30	$1,404.25	$1,404.40