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	$189.33	4.725%	$198.2758	$198.28	$198.30	$198.30
Purchase #2	$89.69	12.131%	$100.5703	$100.57	$100.55	$100.60
Purchase #3	$104.49	6.470%	$111.2505	$111.25	$111.25	$111.30
Purchase #4	$23.71	8.852%	$25.8088	$25.81	$25.80	$25.80
Purchase #5	$157.48	4.349%	$164.3288	$164.33	$164.35	$164.30
Purchase #6	$217.65	13.515%	$247.0654	$247.07	$247.05	$247.10
Purchase #7	$46.52	4.684%	$48.699	$48.70	$48.70	$48.70
7 purchase totals =	$828.87		$895.9986	$896.01	$896.00	$896.10