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	$42.37	5.419%	$44.666	$44.67	$44.65	$44.70
Purchase #2	$137.30	6.348%	$146.0158	$146.02	$146.00	$146.00
Purchase #3	$193.91	12.693%	$218.523	$218.52	$218.50	$218.50
Purchase #4	$65.61	11.117%	$72.9039	$72.90	$72.90	$72.90
Purchase #5	$92.34	12.130%	$103.5408	$103.54	$103.55	$103.50
Purchase #6	$240.28	9.613%	$263.3781	$263.38	$263.40	$263.40
Purchase #7	$107.49	4.151%	$111.9519	$111.95	$111.95	$112.00
7 purchase totals =	$879.30		$960.9795	$960.98	$960.95	$961.00