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	$144.27	5.744%	$152.5569	$152.56	$152.55	$152.60
Purchase #2	$166.66	4.234%	$173.7164	$173.72	$173.70	$173.70
Purchase #3	$229.93	6.420%	$244.6915	$244.69	$244.70	$244.70
Purchase #4	$129.83	10.320%	$143.2285	$143.23	$143.25	$143.20
Purchase #5	$88.85	7.873%	$95.8452	$95.85	$95.85	$95.80
Purchase #6	$98.98	12.219%	$111.0744	$111.07	$111.05	$111.10
Purchase #7	$91.60	10.403%	$101.1291	$101.13	$101.15	$101.10
7 purchase totals =	$950.12		$1,022.2420	$1,022.25	$1,022.25	$1,022.20