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	$199.82	6.183%	$212.1749	$212.17	$212.15	$212.20
Purchase #2	$214.34	3.745%	$222.367	$222.37	$222.35	$222.40
Purchase #3	$46.76	12.559%	$52.6326	$52.63	$52.65	$52.60
Purchase #4	$20.98	3.182%	$21.6476	$21.65	$21.65	$21.60
Purchase #5	$144.86	7.296%	$155.429	$155.43	$155.45	$155.40
Purchase #6	$125.49	3.648%	$130.0679	$130.07	$130.05	$130.10
Purchase #7	$87.58	4.845%	$91.8233	$91.82	$91.80	$91.80
7 purchase totals =	$839.83		$886.1423	$886.14	$886.10	$886.10