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	$86.47	3.440%	$89.4446	$89.44	$89.45	$89.40
Purchase #2	$147.38	12.481%	$165.7745	$165.77	$165.75	$165.80
Purchase #3	$91.77	12.297%	$103.055	$103.06	$103.05	$103.10
Purchase #4	$46.31	6.386%	$49.2674	$49.27	$49.25	$49.30
Purchase #5	$97.76	9.467%	$107.0149	$107.01	$107.00	$107.00
Purchase #6	$26.64	6.563%	$28.3884	$28.39	$28.40	$28.40
Purchase #7	$159.32	8.733%	$173.2334	$173.23	$173.25	$173.20
7 purchase totals =	$655.65		$716.1782	$716.17	$716.15	$716.20