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	$111.75	13.445%	$126.7748	$126.77	$126.75	$126.80
Purchase #2	$127.58	12.296%	$143.2672	$143.27	$143.25	$143.30
Purchase #3	$45.33	7.839%	$48.8834	$48.88	$48.90	$48.90
Purchase #4	$136.36	5.790%	$144.2552	$144.26	$144.25	$144.30
Purchase #5	$85.39	8.243%	$92.4287	$92.43	$92.45	$92.40
Purchase #6	$51.25	9.151%	$55.9399	$55.94	$55.95	$55.90
Purchase #7	$142.69	5.854%	$151.0431	$151.04	$151.05	$151.00
7 purchase totals =	$700.35		$762.5923	$762.59	$762.60	$762.60