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	$56.84	10.323%	$62.7076	$62.71	$62.70	$62.70
Purchase #2	$92.66	8.489%	$100.5259	$100.53	$100.55	$100.50
Purchase #3	$36.52	10.683%	$40.4214	$40.42	$40.40	$40.40
Purchase #4	$224.86	6.265%	$238.9475	$238.95	$238.95	$238.90
Purchase #5	$231.28	9.254%	$252.6827	$252.68	$252.70	$252.70
Purchase #6	$129.48	9.848%	$142.2312	$142.23	$142.25	$142.20
Purchase #7	$86.79	4.619%	$90.7988	$90.80	$90.80	$90.80
7 purchase totals =	$858.43		$928.3151	$928.32	$928.35	$928.20