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	$152.94	3.512%	$158.3113	$158.31	$158.30	$158.30
Purchase #2	$95.89	11.521%	$106.9375	$106.94	$106.95	$106.90
Purchase #3	$9.98	8.486%	$10.8269	$10.83	$10.85	$10.80
Purchase #4	$48.45	12.529%	$54.5203	$54.52	$54.50	$54.50
Purchase #5	$102.81	6.390%	$109.3796	$109.38	$109.40	$109.40
Purchase #6	$51.51	3.775%	$53.4545	$53.45	$53.45	$53.50
Purchase #7	$233.93	10.505%	$258.5043	$258.50	$258.50	$258.50
7 purchase totals =	$695.51		$751.9344	$751.93	$751.95	$751.90