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	$152.54	7.741%	$164.3481	$164.35	$164.35	$164.30
Purchase #2	$200.71	6.708%	$214.1736	$214.17	$214.15	$214.20
Purchase #3	$46.39	12.287%	$52.0899	$52.09	$52.10	$52.10
Purchase #4	$130.51	7.211%	$139.9211	$139.92	$139.90	$139.90
Purchase #5	$126.34	7.679%	$136.0416	$136.04	$136.05	$136.00
Purchase #6	$34.83	6.584%	$37.1232	$37.12	$37.10	$37.10
Purchase #7	$71.57	6.330%	$76.1004	$76.10	$76.10	$76.10
7 purchase totals =	$762.89		$819.7979	$819.79	$819.75	$819.70