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	$164.52	12.874%	$185.7003	$185.70	$185.70	$185.70
Purchase #2	$241.43	13.231%	$273.3736	$273.37	$273.35	$273.40
Purchase #3	$150.54	10.432%	$166.2443	$166.24	$166.25	$166.20
Purchase #4	$95.62	5.521%	$100.8992	$100.90	$100.90	$100.90
Purchase #5	$211.30	4.684%	$221.1973	$221.20	$221.20	$221.20
Purchase #6	$165.96	11.168%	$184.4944	$184.49	$184.50	$184.50
Purchase #7	$12.56	12.702%	$14.1554	$14.16	$14.15	$14.20
7 purchase totals =	$1,041.93		$1,146.0645	$1,146.06	$1,146.05	$1,146.10