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	$58.88	4.450%	$61.5002	$61.50	$61.50	$61.50
Purchase #2	$111.38	4.389%	$116.2685	$116.27	$116.25	$116.30
Purchase #3	$33.58	9.872%	$36.895	$36.90	$36.90	$36.90
Purchase #4	$142.28	6.453%	$151.4613	$151.46	$151.45	$151.50
Purchase #5	$121.64	7.541%	$130.8129	$130.81	$130.80	$130.80
Purchase #6	$9.97	5.466%	$10.515	$10.52	$10.50	$10.50
Purchase #7	$56.60	4.590%	$59.1979	$59.20	$59.20	$59.20
7 purchase totals =	$534.33		$566.6508	$566.66	$566.60	$566.70