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	$137.42	12.171%	$154.1454	$154.15	$154.15	$154.10
Purchase #2	$220.69	4.119%	$229.7802	$229.78	$229.80	$229.80
Purchase #3	$161.66	6.598%	$172.3263	$172.33	$172.35	$172.30
Purchase #4	$154.63	8.402%	$167.622	$167.62	$167.60	$167.60
Purchase #5	$57.97	13.514%	$65.8041	$65.80	$65.80	$65.80
Purchase #6	$165.51	8.303%	$179.2523	$179.25	$179.25	$179.30
Purchase #7	$192.59	3.751%	$199.8141	$199.81	$199.80	$199.80
7 purchase totals =	$1,090.47		$1,168.7444	$1,168.74	$1,168.75	$1,168.70