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	$11.29	5.591%	$11.9212	$11.92	$11.90	$11.90
Purchase #2	$84.86	7.487%	$91.2135	$91.21	$91.20	$91.20
Purchase #3	$68.46	6.144%	$72.6662	$72.67	$72.65	$72.70
Purchase #4	$13.47	7.168%	$14.4355	$14.44	$14.45	$14.40
Purchase #5	$152.77	9.745%	$167.6574	$167.66	$167.65	$167.70
Purchase #6	$158.46	4.456%	$165.521	$165.52	$165.50	$165.50
Purchase #7	$104.77	7.607%	$112.7399	$112.74	$112.75	$112.70
7 purchase totals =	$594.08		$636.1547	$636.16	$636.10	$636.10