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	$112.71	5.153%	$118.5179	$118.52	$118.50	$118.50
Purchase #2	$96.56	5.145%	$101.528	$101.53	$101.55	$101.50
Purchase #3	$111.83	7.861%	$120.621	$120.62	$120.60	$120.60
Purchase #4	$243.86	8.268%	$264.0223	$264.02	$264.00	$264.00
Purchase #5	$80.27	13.848%	$91.3858	$91.39	$91.40	$91.40
Purchase #6	$166.32	4.262%	$173.4086	$173.41	$173.40	$173.40
Purchase #7	$24.46	4.525%	$25.5668	$25.57	$25.55	$25.60
7 purchase totals =	$836.01		$895.0504	$895.06	$895.00	$895.00