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	$99.93	4.737%	$104.6637	$104.66	$104.65	$104.70
Purchase #2	$244.50	3.540%	$253.1553	$253.16	$253.15	$253.20
Purchase #3	$138.43	3.409%	$143.1491	$143.15	$143.15	$143.10
Purchase #4	$21.65	3.343%	$22.3738	$22.37	$22.35	$22.40
Purchase #5	$217.43	3.192%	$224.3704	$224.37	$224.35	$224.40
Purchase #6	$168.39	3.493%	$174.2719	$174.27	$174.25	$174.30
Purchase #7	$129.52	11.461%	$144.3643	$144.36	$144.35	$144.40
7 purchase totals =	$1,019.85		$1,066.3485	$1,066.34	$1,066.25	$1,066.50