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	$71.84	13.713%	$81.6914	$81.69	$81.70	$81.70
Purchase #2	$78.46	12.448%	$88.2267	$88.23	$88.25	$88.20
Purchase #3	$37.93	11.169%	$42.1664	$42.17	$42.15	$42.20
Purchase #4	$200.43	9.442%	$219.3546	$219.35	$219.35	$219.40
Purchase #5	$197.79	11.772%	$221.0738	$221.07	$221.05	$221.10
Purchase #6	$197.42	6.707%	$210.661	$210.66	$210.65	$210.70
Purchase #7	$85.30	4.497%	$89.1359	$89.14	$89.15	$89.10
7 purchase totals =	$869.17		$952.3098	$952.31	$952.30	$952.40