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	$217.49	10.872%	$241.1355	$241.14	$241.15	$241.10
Purchase #2	$172.54	10.555%	$190.7516	$190.75	$190.75	$190.80
Purchase #3	$169.92	8.802%	$184.8764	$184.88	$184.90	$184.90
Purchase #4	$151.41	10.582%	$167.4322	$167.43	$167.45	$167.40
Purchase #5	$8.53	3.547%	$8.8326	$8.83	$8.85	$8.80
Purchase #6	$139.98	4.780%	$146.671	$146.67	$146.65	$146.70
Purchase #7	$158.82	12.872%	$179.2633	$179.26	$179.25	$179.30
7 purchase totals =	$1,018.69		$1,118.9626	$1,118.96	$1,119.00	$1,119.00