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	$133.53	7.463%	$143.4953	$143.50	$143.50	$143.50
Purchase #2	$118.93	6.860%	$127.0886	$127.09	$127.10	$127.10
Purchase #3	$158.25	4.778%	$165.8112	$165.81	$165.80	$165.80
Purchase #4	$126.81	7.591%	$136.4361	$136.44	$136.45	$136.40
Purchase #5	$142.39	11.229%	$158.379	$158.38	$158.40	$158.40
Purchase #6	$62.64	3.325%	$64.7228	$64.72	$64.70	$64.70
Purchase #7	$196.80	12.257%	$220.9218	$220.92	$220.90	$220.90
7 purchase totals =	$939.35		$1,016.8548	$1,016.86	$1,016.85	$1,016.80