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	$157.51	9.585%	$172.6073	$172.61	$172.60	$172.60
Purchase #2	$135.99	7.822%	$146.6271	$146.63	$146.65	$146.60
Purchase #3	$160.91	4.726%	$168.5146	$168.51	$168.50	$168.50
Purchase #4	$249.65	10.790%	$276.5872	$276.59	$276.60	$276.60
Purchase #5	$145.53	3.431%	$150.5231	$150.52	$150.50	$150.50
Purchase #6	$148.52	13.574%	$168.6801	$168.68	$168.70	$168.70
Purchase #7	$188.30	13.864%	$214.4059	$214.41	$214.40	$214.40
7 purchase totals =	$1,186.41		$1,297.9453	$1,297.95	$1,297.95	$1,297.90