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	$165.26	12.263%	$185.5258	$185.53	$185.55	$185.50
Purchase #2	$119.82	6.367%	$127.4489	$127.45	$127.45	$127.40
Purchase #3	$200.43	11.840%	$224.1609	$224.16	$224.15	$224.20
Purchase #4	$51.27	3.383%	$53.0045	$53.00	$53.00	$53.00
Purchase #5	$238.55	12.602%	$268.6121	$268.61	$268.60	$268.60
Purchase #6	$89.92	5.244%	$94.6354	$94.64	$94.65	$94.60
Purchase #7	$9.92	10.848%	$10.9961	$11.00	$11.00	$11.00
7 purchase totals =	$875.17		$964.3837	$964.39	$964.40	$964.30