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	$210.86	5.335%	$222.1094	$222.11	$222.10	$222.10
Purchase #2	$208.30	8.753%	$226.5325	$226.53	$226.55	$226.50
Purchase #3	$139.82	7.404%	$150.1723	$150.17	$150.15	$150.20
Purchase #4	$81.38	9.836%	$89.3845	$89.38	$89.40	$89.40
Purchase #5	$130.79	11.233%	$145.4816	$145.48	$145.50	$145.50
Purchase #6	$136.79	13.536%	$155.3059	$155.31	$155.30	$155.30
Purchase #7	$35.99	6.713%	$38.406	$38.41	$38.40	$38.40
7 purchase totals =	$943.93		$1,027.3922	$1,027.39	$1,027.40	$1,027.40