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	$176.37	13.649%	$200.4427	$200.44	$200.45	$200.40
Purchase #2	$42.86	5.140%	$45.063	$45.06	$45.05	$45.10
Purchase #3	$248.77	4.181%	$259.1711	$259.17	$259.15	$259.20
Purchase #4	$218.87	11.524%	$244.0926	$244.09	$244.10	$244.10
Purchase #5	$16.46	13.243%	$18.6398	$18.64	$18.65	$18.60
Purchase #6	$120.69	5.726%	$127.6007	$127.60	$127.60	$127.60
Purchase #7	$241.74	4.779%	$253.2928	$253.29	$253.30	$253.30
7 purchase totals =	$1,065.76		$1,148.3027	$1,148.29	$1,148.30	$1,148.30