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	$242.30	12.160%	$271.7637	$271.76	$271.75	$271.80
Purchase #2	$38.83	8.176%	$42.0047	$42.00	$42.00	$42.00
Purchase #3	$54.31	11.119%	$60.3487	$60.35	$60.35	$60.30
Purchase #4	$101.75	9.227%	$111.1385	$111.14	$111.15	$111.10
Purchase #5	$172.55	3.241%	$178.1423	$178.14	$178.15	$178.10
Purchase #6	$243.84	13.139%	$275.8781	$275.88	$275.90	$275.90
Purchase #7	$225.56	4.366%	$235.4079	$235.41	$235.40	$235.40
7 purchase totals =	$1,079.14		$1,174.6839	$1,174.68	$1,174.70	$1,174.60