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	$117.47	8.407%	$127.3457	$127.35	$127.35	$127.30
Purchase #2	$152.92	4.298%	$159.4925	$159.49	$159.50	$159.50
Purchase #3	$141.38	4.149%	$147.2459	$147.25	$147.25	$147.20
Purchase #4	$77.97	5.840%	$82.5234	$82.52	$82.50	$82.50
Purchase #5	$246.83	11.772%	$275.8868	$275.89	$275.90	$275.90
Purchase #6	$129.34	10.447%	$142.8521	$142.85	$142.85	$142.90
Purchase #7	$196.56	13.761%	$223.6086	$223.61	$223.60	$223.60
7 purchase totals =	$1,062.47		$1,158.9550	$1,158.96	$1,158.95	$1,158.90