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	$155.82	9.150%	$170.0775	$170.08	$170.10	$170.10
Purchase #2	$46.27	13.557%	$52.5428	$52.54	$52.55	$52.50
Purchase #3	$229.59	5.250%	$241.6435	$241.64	$241.65	$241.60
Purchase #4	$171.73	3.418%	$177.5997	$177.60	$177.60	$177.60
Purchase #5	$175.75	10.136%	$193.564	$193.56	$193.55	$193.60
Purchase #6	$178.42	6.730%	$190.4277	$190.43	$190.45	$190.40
Purchase #7	$90.75	10.538%	$100.3132	$100.31	$100.30	$100.30
7 purchase totals =	$1,048.33		$1,126.1684	$1,126.16	$1,126.20	$1,126.10