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	$143.45	3.700%	$148.7577	$148.76	$148.75	$148.80
Purchase #2	$192.34	12.128%	$215.667	$215.67	$215.65	$215.70
Purchase #3	$115.96	9.370%	$126.8255	$126.83	$126.85	$126.80
Purchase #4	$193.59	7.706%	$208.508	$208.51	$208.50	$208.50
Purchase #5	$101.92	10.760%	$112.8866	$112.89	$112.90	$112.90
Purchase #6	$159.74	12.344%	$179.4583	$179.46	$179.45	$179.50
Purchase #7	$131.97	9.445%	$144.4346	$144.43	$144.45	$144.40
7 purchase totals =	$1,038.97		$1,136.5377	$1,136.55	$1,136.55	$1,136.60