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	$199.70	11.405%	$222.4758	$222.48	$222.50	$222.50
Purchase #2	$111.45	4.156%	$116.0819	$116.08	$116.10	$116.10
Purchase #3	$136.39	12.472%	$153.4006	$153.40	$153.40	$153.40
Purchase #4	$90.78	11.510%	$101.2288	$101.23	$101.25	$101.20
Purchase #5	$54.92	4.199%	$57.2261	$57.23	$57.25	$57.20
Purchase #6	$112.51	11.275%	$125.1955	$125.20	$125.20	$125.20
Purchase #7	$29.28	5.454%	$30.8769	$30.88	$30.90	$30.90
7 purchase totals =	$735.03		$806.4856	$806.50	$806.60	$806.50