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	$97.65	9.151%	$106.586	$106.59	$106.60	$106.60
Purchase #2	$171.32	4.220%	$178.5497	$178.55	$178.55	$178.50
Purchase #3	$52.51	5.623%	$55.4626	$55.46	$55.45	$55.50
Purchase #4	$222.56	4.844%	$233.3408	$233.34	$233.35	$233.30
Purchase #5	$173.50	3.374%	$179.3539	$179.35	$179.35	$179.40
Purchase #6	$60.69	9.255%	$66.3069	$66.31	$66.30	$66.30
Purchase #7	$143.25	5.803%	$151.5628	$151.56	$151.55	$151.60
7 purchase totals =	$921.48		$971.1627	$971.16	$971.15	$971.20