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	$248.35	7.218%	$266.2759	$266.28	$266.30	$266.30
Purchase #2	$175.60	8.228%	$190.0484	$190.05	$190.05	$190.00
Purchase #3	$18.98	7.156%	$20.3382	$20.34	$20.35	$20.30
Purchase #4	$130.62	13.187%	$147.8449	$147.84	$147.85	$147.80
Purchase #5	$80.79	3.316%	$83.469	$83.47	$83.45	$83.50
Purchase #6	$103.57	7.343%	$111.1751	$111.18	$111.20	$111.20
Purchase #7	$54.38	3.396%	$56.2267	$56.23	$56.25	$56.20
7 purchase totals =	$812.29		$875.3782	$875.39	$875.45	$875.30