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	$43.78	7.865%	$47.2233	$47.22	$47.20	$47.20
Purchase #2	$165.91	9.428%	$181.552	$181.55	$181.55	$181.60
Purchase #3	$241.26	11.595%	$269.2341	$269.23	$269.25	$269.20
Purchase #4	$141.72	11.110%	$157.4651	$157.47	$157.45	$157.50
Purchase #5	$151.70	3.377%	$156.8229	$156.82	$156.80	$156.80
Purchase #6	$184.79	11.476%	$205.9965	$206.00	$206.00	$206.00
Purchase #7	$120.41	10.124%	$132.6003	$132.60	$132.60	$132.60
7 purchase totals =	$1,049.57		$1,150.8942	$1,150.89	$1,150.85	$1,150.90