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	$210.87	10.604%	$233.2307	$233.23	$233.25	$233.20
Purchase #2	$225.60	13.381%	$255.7875	$255.79	$255.80	$255.80
Purchase #3	$74.47	5.551%	$78.6038	$78.60	$78.60	$78.60
Purchase #4	$104.63	9.505%	$114.5751	$114.58	$114.60	$114.60
Purchase #5	$210.66	6.710%	$224.7953	$224.80	$224.80	$224.80
Purchase #6	$111.34	10.565%	$123.1031	$123.10	$123.10	$123.10
Purchase #7	$7.29	5.491%	$7.6903	$7.69	$7.70	$7.70
7 purchase totals =	$944.86		$1,037.7858	$1,037.79	$1,037.85	$1,037.80