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	$77.46	8.586%	$84.1107	$84.11	$84.10	$84.10
Purchase #2	$242.89	7.572%	$261.2816	$261.28	$261.30	$261.30
Purchase #3	$19.83	12.281%	$22.2653	$22.27	$22.25	$22.30
Purchase #4	$237.73	7.322%	$255.1366	$255.14	$255.15	$255.10
Purchase #5	$175.97	13.826%	$200.2996	$200.30	$200.30	$200.30
Purchase #6	$102.52	8.701%	$111.4403	$111.44	$111.45	$111.40
Purchase #7	$113.34	12.490%	$127.4962	$127.50	$127.50	$127.50
7 purchase totals =	$969.74		$1,062.0303	$1,062.04	$1,062.05	$1,062.00