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	$205.31	5.495%	$216.5918	$216.59	$216.60	$216.60
Purchase #2	$93.43	7.599%	$100.5297	$100.53	$100.55	$100.50
Purchase #3	$115.60	12.501%	$130.0512	$130.05	$130.05	$130.10
Purchase #4	$137.91	5.309%	$145.2316	$145.23	$145.25	$145.20
Purchase #5	$127.40	3.383%	$131.7099	$131.71	$131.70	$131.70
Purchase #6	$127.38	12.509%	$143.314	$143.31	$143.30	$143.30
Purchase #7	$77.77	11.614%	$86.8022	$86.80	$86.80	$86.80
7 purchase totals =	$884.80		$954.2304	$954.22	$954.25	$954.20