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	$67.91	4.169%	$70.7412	$70.74	$70.75	$70.70
Purchase #2	$58.32	3.622%	$60.4324	$60.43	$60.45	$60.40
Purchase #3	$248.97	13.615%	$282.8673	$282.87	$282.85	$282.90
Purchase #4	$34.86	6.623%	$37.1688	$37.17	$37.15	$37.20
Purchase #5	$191.45	6.504%	$203.9019	$203.90	$203.90	$203.90
Purchase #6	$54.35	9.456%	$59.4893	$59.49	$59.50	$59.50
Purchase #7	$144.99	4.528%	$151.5551	$151.56	$151.55	$151.60
7 purchase totals =	$800.85		$866.1560	$866.16	$866.15	$866.20