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	$82.76	3.203%	$85.4108	$85.41	$85.40	$85.40
Purchase #2	$20.40	5.479%	$21.5177	$21.52	$21.50	$21.50
Purchase #3	$155.32	11.360%	$172.9644	$172.96	$172.95	$173.00
Purchase #4	$18.40	3.418%	$19.0289	$19.03	$19.05	$19.00
Purchase #5	$51.88	7.255%	$55.6439	$55.64	$55.65	$55.60
Purchase #6	$199.35	9.541%	$218.37	$218.37	$218.35	$218.40
Purchase #7	$242.85	13.478%	$275.5813	$275.58	$275.60	$275.60
7 purchase totals =	$770.96		$848.5170	$848.51	$848.50	$848.50