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	$55.71	10.377%	$61.491	$61.49	$61.50	$61.50
Purchase #2	$14.61	6.530%	$15.564	$15.56	$15.55	$15.60
Purchase #3	$91.68	9.523%	$100.4107	$100.41	$100.40	$100.40
Purchase #4	$59.51	3.303%	$61.4756	$61.48	$61.50	$61.50
Purchase #5	$34.42	6.369%	$36.6122	$36.61	$36.60	$36.60
Purchase #6	$126.43	5.410%	$133.2699	$133.27	$133.25	$133.30
Purchase #7	$228.70	5.317%	$240.86	$240.86	$240.85	$240.90
7 purchase totals =	$611.06		$649.6834	$649.68	$649.65	$649.80