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	$209.80	11.467%	$233.8578	$233.86	$233.85	$233.90
Purchase #2	$146.67	7.218%	$157.2566	$157.26	$157.25	$157.30
Purchase #3	$144.80	12.238%	$162.5206	$162.52	$162.50	$162.50
Purchase #4	$150.49	7.730%	$162.1229	$162.12	$162.10	$162.10
Purchase #5	$40.83	4.811%	$42.7943	$42.79	$42.80	$42.80
Purchase #6	$151.41	10.465%	$167.2551	$167.26	$167.25	$167.30
Purchase #7	$19.80	11.345%	$22.0463	$22.05	$22.05	$22.00
7 purchase totals =	$863.80		$947.8536	$947.86	$947.80	$947.90