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	$92.68	13.788%	$105.4587	$105.46	$105.45	$105.50
Purchase #2	$192.28	10.855%	$213.152	$213.15	$213.15	$213.20
Purchase #3	$241.28	5.793%	$255.2574	$255.26	$255.25	$255.30
Purchase #4	$166.50	10.122%	$183.3531	$183.35	$183.35	$183.40
Purchase #5	$48.91	6.550%	$52.1136	$52.11	$52.10	$52.10
Purchase #6	$151.48	4.490%	$158.2815	$158.28	$158.30	$158.30
Purchase #7	$144.82	12.505%	$162.9297	$162.93	$162.95	$162.90
7 purchase totals =	$1,037.95		$1,130.5460	$1,130.54	$1,130.55	$1,130.70