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	$146.48	6.173%	$155.5222	$155.52	$155.50	$155.50
Purchase #2	$52.39	4.176%	$54.5778	$54.58	$54.60	$54.60
Purchase #3	$91.37	13.117%	$103.355	$103.36	$103.35	$103.40
Purchase #4	$216.26	3.161%	$223.096	$223.10	$223.10	$223.10
Purchase #5	$236.76	13.193%	$267.9957	$268.00	$268.00	$268.00
Purchase #6	$27.31	6.406%	$29.0595	$29.06	$29.05	$29.10
Purchase #7	$206.25	13.423%	$233.9349	$233.93	$233.95	$233.90
7 purchase totals =	$976.82		$1,067.5411	$1,067.55	$1,067.55	$1,067.60