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	$43.43	3.852%	$45.1029	$45.10	$45.10	$45.10
Purchase #2	$20.53	6.174%	$21.7975	$21.80	$21.80	$21.80
Purchase #3	$72.56	7.847%	$78.2538	$78.25	$78.25	$78.30
Purchase #4	$46.49	8.219%	$50.311	$50.31	$50.30	$50.30
Purchase #5	$244.66	9.309%	$267.4354	$267.44	$267.45	$267.40
Purchase #6	$200.61	6.826%	$214.3036	$214.30	$214.30	$214.30
Purchase #7	$160.55	5.297%	$169.0543	$169.05	$169.05	$169.10
7 purchase totals =	$788.83		$846.2585	$846.25	$846.25	$846.30