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	$215.68	11.845%	$241.2273	$241.23	$241.25	$241.20
Purchase #2	$30.43	4.237%	$31.7193	$31.72	$31.70	$31.70
Purchase #3	$80.80	10.313%	$89.1329	$89.13	$89.15	$89.10
Purchase #4	$166.76	4.303%	$173.9357	$173.94	$173.95	$173.90
Purchase #5	$150.44	11.155%	$167.2216	$167.22	$167.20	$167.20
Purchase #6	$210.51	7.747%	$226.8182	$226.82	$226.80	$226.80
Purchase #7	$190.92	13.855%	$217.372	$217.37	$217.35	$217.40
7 purchase totals =	$1,045.54		$1,147.4270	$1,147.43	$1,147.40	$1,147.30