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	$96.49	4.715%	$101.0395	$101.04	$101.05	$101.00
Purchase #2	$127.50	10.693%	$141.1336	$141.13	$141.15	$141.10
Purchase #3	$202.74	7.446%	$217.836	$217.84	$217.85	$217.80
Purchase #4	$129.56	11.317%	$144.2223	$144.22	$144.20	$144.20
Purchase #5	$35.56	8.763%	$38.6761	$38.68	$38.70	$38.70
Purchase #6	$144.89	9.663%	$158.8907	$158.89	$158.90	$158.90
Purchase #7	$90.36	13.530%	$102.5857	$102.59	$102.60	$102.60
7 purchase totals =	$827.10		$904.3839	$904.39	$904.45	$904.30