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	$233.69	9.151%	$255.075	$255.08	$255.10	$255.10
Purchase #2	$85.95	3.380%	$88.8551	$88.86	$88.85	$88.90
Purchase #3	$149.69	11.155%	$166.3879	$166.39	$166.40	$166.40
Purchase #4	$114.72	12.823%	$129.4305	$129.43	$129.45	$129.40
Purchase #5	$211.95	6.116%	$224.9129	$224.91	$224.90	$224.90
Purchase #6	$48.39	7.748%	$52.1393	$52.14	$52.15	$52.10
Purchase #7	$139.81	6.480%	$148.8697	$148.87	$148.85	$148.90
7 purchase totals =	$984.20		$1,065.6704	$1,065.68	$1,065.70	$1,065.70