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	$181.35	3.723%	$188.1017	$188.10	$188.10	$188.10
Purchase #2	$196.28	9.605%	$215.1327	$215.13	$215.15	$215.10
Purchase #3	$60.29	11.729%	$67.3614	$67.36	$67.35	$67.40
Purchase #4	$150.29	5.285%	$158.2328	$158.23	$158.25	$158.20
Purchase #5	$174.42	9.389%	$190.7963	$190.80	$190.80	$190.80
Purchase #6	$102.72	11.550%	$114.5842	$114.58	$114.60	$114.60
Purchase #7	$142.73	6.454%	$151.9418	$151.94	$151.95	$151.90
7 purchase totals =	$1,008.08		$1,086.1509	$1,086.14	$1,086.20	$1,086.10