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	$76.64	12.382%	$86.1296	$86.13	$86.15	$86.10
Purchase #2	$105.79	5.612%	$111.7269	$111.73	$111.75	$111.70
Purchase #3	$17.38	10.774%	$19.2525	$19.25	$19.25	$19.30
Purchase #4	$236.27	3.485%	$244.504	$244.50	$244.50	$244.50
Purchase #5	$158.34	11.553%	$176.633	$176.63	$176.65	$176.60
Purchase #6	$195.97	13.376%	$222.1829	$222.18	$222.20	$222.20
Purchase #7	$12.41	11.736%	$13.8664	$13.87	$13.85	$13.90
7 purchase totals =	$802.80		$874.2953	$874.29	$874.35	$874.30