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	$248.74	7.622%	$267.699	$267.70	$267.70	$267.70
Purchase #2	$229.75	3.587%	$237.9911	$237.99	$238.00	$238.00
Purchase #3	$29.59	8.325%	$32.0534	$32.05	$32.05	$32.10
Purchase #4	$90.25	10.300%	$99.5458	$99.55	$99.55	$99.50
Purchase #5	$69.92	12.170%	$78.4293	$78.43	$78.45	$78.40
Purchase #6	$222.37	6.719%	$237.311	$237.31	$237.30	$237.30
Purchase #7	$57.45	10.539%	$63.5047	$63.50	$63.50	$63.50
7 purchase totals =	$948.07		$1,016.5343	$1,016.53	$1,016.55	$1,016.50