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	$146.87	3.169%	$151.5243	$151.52	$151.50	$151.50
Purchase #2	$183.46	10.723%	$203.1324	$203.13	$203.15	$203.10
Purchase #3	$64.88	10.710%	$71.8286	$71.83	$71.85	$71.80
Purchase #4	$141.30	8.373%	$153.131	$153.13	$153.15	$153.10
Purchase #5	$215.98	12.197%	$242.3231	$242.32	$242.30	$242.30
Purchase #6	$152.69	3.766%	$158.4403	$158.44	$158.45	$158.40
Purchase #7	$88.49	13.483%	$100.4211	$100.42	$100.40	$100.40
7 purchase totals =	$993.67		$1,080.8008	$1,080.79	$1,080.80	$1,080.60