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	$134.79	10.518%	$148.9672	$148.97	$148.95	$149.00
Purchase #2	$116.64	12.760%	$131.5233	$131.52	$131.50	$131.50
Purchase #3	$93.37	13.671%	$106.1346	$106.13	$106.15	$106.10
Purchase #4	$164.66	9.168%	$179.756	$179.76	$179.75	$179.80
Purchase #5	$129.54	11.600%	$144.5666	$144.57	$144.55	$144.60
Purchase #6	$42.87	5.295%	$45.14	$45.14	$45.15	$45.10
Purchase #7	$76.30	6.755%	$81.4541	$81.45	$81.45	$81.50
7 purchase totals =	$758.17		$837.5418	$837.54	$837.50	$837.60