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	$247.25	3.227%	$255.2288	$255.23	$255.25	$255.20
Purchase #2	$63.75	3.242%	$65.8168	$65.82	$65.80	$65.80
Purchase #3	$118.64	7.203%	$127.1856	$127.19	$127.20	$127.20
Purchase #4	$244.45	7.184%	$262.0113	$262.01	$262.00	$262.00
Purchase #5	$216.64	13.754%	$246.4367	$246.44	$246.45	$246.40
Purchase #6	$165.91	3.418%	$171.5808	$171.58	$171.60	$171.60
Purchase #7	$100.51	13.529%	$114.108	$114.11	$114.10	$114.10
7 purchase totals =	$1,157.15		$1,242.3680	$1,242.38	$1,242.40	$1,242.30