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	$199.33	4.284%	$207.8693	$207.87	$207.85	$207.90
Purchase #2	$204.35	12.566%	$230.0286	$230.03	$230.05	$230.00
Purchase #3	$57.57	7.510%	$61.8935	$61.89	$61.90	$61.90
Purchase #4	$128.41	13.639%	$145.9238	$145.92	$145.90	$145.90
Purchase #5	$60.87	6.331%	$64.7237	$64.72	$64.70	$64.70
Purchase #6	$230.97	10.375%	$254.9331	$254.93	$254.95	$254.90
Purchase #7	$88.95	7.840%	$95.9237	$95.92	$95.90	$95.90
7 purchase totals =	$970.45		$1,061.2957	$1,061.28	$1,061.25	$1,061.20