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	$94.99	6.167%	$100.848	$100.85	$100.85	$100.80
Purchase #2	$236.97	4.771%	$248.2758	$248.28	$248.30	$248.30
Purchase #3	$108.49	9.610%	$118.9159	$118.92	$118.90	$118.90
Purchase #4	$151.53	13.750%	$172.3654	$172.37	$172.35	$172.40
Purchase #5	$112.53	11.494%	$125.4642	$125.46	$125.45	$125.50
Purchase #6	$159.36	5.421%	$167.9989	$168.00	$168.00	$168.00
Purchase #7	$107.51	3.261%	$111.0159	$111.02	$111.00	$111.00
7 purchase totals =	$971.38		$1,044.8841	$1,044.90	$1,044.85	$1,044.90