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	$195.75	7.840%	$211.0968	$211.10	$211.10	$211.10
Purchase #2	$73.42	13.687%	$83.469	$83.47	$83.45	$83.50
Purchase #3	$67.72	7.647%	$72.8985	$72.90	$72.90	$72.90
Purchase #4	$148.34	3.714%	$153.8493	$153.85	$153.85	$153.80
Purchase #5	$216.79	11.429%	$241.5669	$241.57	$241.55	$241.60
Purchase #6	$143.75	3.363%	$148.5843	$148.58	$148.60	$148.60
Purchase #7	$61.84	13.754%	$70.3455	$70.35	$70.35	$70.30
7 purchase totals =	$907.61		$981.8103	$981.82	$981.80	$981.80