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	$135.43	7.497%	$145.5832	$145.58	$145.60	$145.60
Purchase #2	$83.43	8.783%	$90.7577	$90.76	$90.75	$90.80
Purchase #3	$11.31	9.563%	$12.3916	$12.39	$12.40	$12.40
Purchase #4	$247.79	13.240%	$280.5974	$280.60	$280.60	$280.60
Purchase #5	$177.88	5.784%	$188.1686	$188.17	$188.15	$188.20
Purchase #6	$97.99	5.640%	$103.5166	$103.52	$103.50	$103.50
Purchase #7	$191.84	4.251%	$199.9951	$200.00	$200.00	$200.00
7 purchase totals =	$945.67		$1,021.0102	$1,021.02	$1,021.00	$1,021.10