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	$233.46	6.493%	$248.6186	$248.62	$248.60	$248.60
Purchase #2	$103.31	11.310%	$114.9944	$114.99	$115.00	$115.00
Purchase #3	$91.86	8.160%	$99.3558	$99.36	$99.35	$99.40
Purchase #4	$119.89	6.401%	$127.5642	$127.56	$127.55	$127.60
Purchase #5	$243.28	13.251%	$275.517	$275.52	$275.50	$275.50
Purchase #6	$45.33	6.746%	$48.388	$48.39	$48.40	$48.40
Purchase #7	$97.78	8.762%	$106.3475	$106.35	$106.35	$106.30
7 purchase totals =	$934.91		$1,020.7855	$1,020.79	$1,020.75	$1,020.80