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	$12.37	13.662%	$14.06	$14.06	$14.05	$14.10
Purchase #2	$17.27	7.223%	$18.5174	$18.52	$18.50	$18.50
Purchase #3	$157.75	4.766%	$165.2684	$165.27	$165.25	$165.30
Purchase #4	$48.29	12.260%	$54.2104	$54.21	$54.20	$54.20
Purchase #5	$221.74	9.552%	$242.9206	$242.92	$242.90	$242.90
Purchase #6	$157.40	6.654%	$167.8734	$167.87	$167.85	$167.90
Purchase #7	$94.74	9.543%	$103.781	$103.78	$103.80	$103.80
7 purchase totals =	$709.56		$766.6312	$766.63	$766.55	$766.70