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	$213.48	4.403%	$222.8795	$222.88	$222.90	$222.90
Purchase #2	$44.83	7.711%	$48.2868	$48.29	$48.30	$48.30
Purchase #3	$103.57	6.250%	$110.0431	$110.04	$110.05	$110.00
Purchase #4	$130.53	11.323%	$145.3099	$145.31	$145.30	$145.30
Purchase #5	$18.99	8.114%	$20.5308	$20.53	$20.55	$20.50
Purchase #6	$65.51	7.113%	$70.1697	$70.17	$70.15	$70.20
Purchase #7	$141.55	4.805%	$148.3515	$148.35	$148.35	$148.40
7 purchase totals =	$718.46		$765.5713	$765.57	$765.60	$765.60