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	$183.62	3.657%	$190.335	$190.34	$190.35	$190.30
Purchase #2	$111.71	5.614%	$117.9814	$117.98	$118.00	$118.00
Purchase #3	$181.52	10.668%	$200.8846	$200.88	$200.90	$200.90
Purchase #4	$125.78	11.122%	$139.7693	$139.77	$139.75	$139.80
Purchase #5	$146.31	10.121%	$161.118	$161.12	$161.10	$161.10
Purchase #6	$206.64	4.339%	$215.6061	$215.61	$215.60	$215.60
Purchase #7	$62.68	12.327%	$70.4066	$70.41	$70.40	$70.40
7 purchase totals =	$1,018.26		$1,096.1010	$1,096.11	$1,096.10	$1,096.10