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	$68.92	6.810%	$73.6135	$73.61	$73.60	$73.60
Purchase #2	$110.38	11.595%	$123.1786	$123.18	$123.20	$123.20
Purchase #3	$109.30	13.195%	$123.7221	$123.72	$123.70	$123.70
Purchase #4	$230.88	6.139%	$245.0537	$245.05	$245.05	$245.10
Purchase #5	$50.66	6.594%	$54.0005	$54.00	$54.00	$54.00
Purchase #6	$165.45	9.326%	$180.8799	$180.88	$180.90	$180.90
Purchase #7	$155.85	6.157%	$165.4457	$165.45	$165.45	$165.40
7 purchase totals =	$891.44		$965.8940	$965.89	$965.90	$965.90