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	$39.75	9.702%	$43.6065	$43.61	$43.60	$43.60
Purchase #2	$18.49	5.110%	$19.4348	$19.43	$19.45	$19.40
Purchase #3	$232.75	6.143%	$247.0478	$247.05	$247.05	$247.00
Purchase #4	$102.51	6.541%	$109.2152	$109.22	$109.20	$109.20
Purchase #5	$72.72	7.375%	$78.0831	$78.08	$78.10	$78.10
Purchase #6	$223.97	9.433%	$245.0971	$245.10	$245.10	$245.10
Purchase #7	$246.78	10.552%	$272.8202	$272.82	$272.80	$272.80
7 purchase totals =	$936.97		$1,015.3047	$1,015.31	$1,015.30	$1,015.20