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	$145.42	8.580%	$157.897	$157.90	$157.90	$157.90
Purchase #2	$32.99	9.190%	$36.0218	$36.02	$36.00	$36.00
Purchase #3	$222.34	10.712%	$246.1571	$246.16	$246.15	$246.20
Purchase #4	$32.60	10.495%	$36.0214	$36.02	$36.00	$36.00
Purchase #5	$26.32	4.860%	$27.5992	$27.60	$27.60	$27.60
Purchase #6	$99.61	11.797%	$111.361	$111.36	$111.35	$111.40
Purchase #7	$146.60	3.852%	$152.247	$152.25	$152.25	$152.20
7 purchase totals =	$705.88		$767.3045	$767.31	$767.25	$767.30