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	$246.96	8.623%	$268.2554	$268.26	$268.25	$268.30
Purchase #2	$37.43	5.546%	$39.5059	$39.51	$39.50	$39.50
Purchase #3	$154.28	9.118%	$168.3473	$168.35	$168.35	$168.30
Purchase #4	$148.79	13.243%	$168.4943	$168.49	$168.50	$168.50
Purchase #5	$137.47	9.384%	$150.3702	$150.37	$150.35	$150.40
Purchase #6	$168.41	7.283%	$180.6753	$180.68	$180.70	$180.70
Purchase #7	$151.74	10.438%	$167.5786	$167.58	$167.60	$167.60
7 purchase totals =	$1,045.08		$1,143.2270	$1,143.24	$1,143.25	$1,143.30