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	$97.57	5.820%	$103.2486	$103.25	$103.25	$103.20
Purchase #2	$37.38	5.693%	$39.508	$39.51	$39.50	$39.50
Purchase #3	$194.40	13.343%	$220.3388	$220.34	$220.35	$220.30
Purchase #4	$85.28	10.523%	$94.254	$94.25	$94.25	$94.30
Purchase #5	$27.58	7.104%	$29.5393	$29.54	$29.55	$29.50
Purchase #6	$12.56	7.456%	$13.4965	$13.50	$13.50	$13.50
Purchase #7	$236.54	3.209%	$244.1306	$244.13	$244.15	$244.10
7 purchase totals =	$691.31		$744.5158	$744.52	$744.55	$744.40