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	$48.90	6.462%	$52.0599	$52.06	$52.05	$52.10
Purchase #2	$90.43	12.701%	$101.9155	$101.92	$101.90	$101.90
Purchase #3	$48.27	3.150%	$49.7905	$49.79	$49.80	$49.80
Purchase #4	$84.70	4.851%	$88.8088	$88.81	$88.80	$88.80
Purchase #5	$188.38	4.135%	$196.1695	$196.17	$196.15	$196.20
Purchase #6	$12.90	9.834%	$14.1686	$14.17	$14.15	$14.20
Purchase #7	$153.38	10.465%	$169.4312	$169.43	$169.45	$169.40
7 purchase totals =	$626.96		$672.3440	$672.35	$672.30	$672.40