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	$112.88	11.764%	$126.1592	$126.16	$126.15	$126.20
Purchase #2	$100.44	10.816%	$111.3036	$111.30	$111.30	$111.30
Purchase #3	$170.69	13.583%	$193.8748	$193.87	$193.85	$193.90
Purchase #4	$113.36	3.372%	$117.1825	$117.18	$117.20	$117.20
Purchase #5	$84.78	11.614%	$94.6263	$94.63	$94.65	$94.60
Purchase #6	$54.78	8.227%	$59.2868	$59.29	$59.30	$59.30
Purchase #7	$213.63	8.165%	$231.0729	$231.07	$231.05	$231.10
7 purchase totals =	$850.56		$933.5061	$933.50	$933.50	$933.60