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	$48.37	3.622%	$50.122	$50.12	$50.10	$50.10
Purchase #2	$56.85	3.814%	$59.0183	$59.02	$59.00	$59.00
Purchase #3	$193.79	12.431%	$217.88	$217.88	$217.90	$217.90
Purchase #4	$72.86	12.763%	$82.1591	$82.16	$82.15	$82.20
Purchase #5	$236.42	5.822%	$250.1844	$250.18	$250.20	$250.20
Purchase #6	$149.90	10.551%	$165.7159	$165.72	$165.70	$165.70
Purchase #7	$233.28	11.151%	$259.2931	$259.29	$259.30	$259.30
7 purchase totals =	$991.47		$1,084.3728	$1,084.37	$1,084.35	$1,084.40