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	$181.68	3.398%	$187.8535	$187.85	$187.85	$187.90
Purchase #2	$15.45	4.352%	$16.1224	$16.12	$16.10	$16.10
Purchase #3	$105.83	13.470%	$120.0853	$120.09	$120.10	$120.10
Purchase #4	$38.50	3.111%	$39.6977	$39.70	$39.70	$39.70
Purchase #5	$136.51	10.140%	$150.3521	$150.35	$150.35	$150.40
Purchase #6	$58.62	4.317%	$61.1506	$61.15	$61.15	$61.20
Purchase #7	$81.88	12.621%	$92.2141	$92.21	$92.20	$92.20
7 purchase totals =	$618.47		$667.4757	$667.47	$667.45	$667.60