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	$224.88	8.656%	$244.3456	$244.35	$244.35	$244.30
Purchase #2	$118.63	10.224%	$130.7587	$130.76	$130.75	$130.80
Purchase #3	$234.97	10.588%	$259.8486	$259.85	$259.85	$259.80
Purchase #4	$65.79	10.227%	$72.5183	$72.52	$72.50	$72.50
Purchase #5	$167.75	10.846%	$185.9442	$185.94	$185.95	$185.90
Purchase #6	$183.56	10.416%	$202.6796	$202.68	$202.70	$202.70
Purchase #7	$13.67	13.313%	$15.4899	$15.49	$15.50	$15.50
7 purchase totals =	$1,009.25		$1,111.5849	$1,111.59	$1,111.60	$1,111.50