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	$226.28	7.159%	$242.4794	$242.48	$242.50	$242.50
Purchase #2	$218.65	5.306%	$230.2516	$230.25	$230.25	$230.30
Purchase #3	$89.72	11.683%	$100.202	$100.20	$100.20	$100.20
Purchase #4	$101.89	12.792%	$114.9238	$114.92	$114.90	$114.90
Purchase #5	$203.36	10.141%	$223.9827	$223.98	$224.00	$224.00
Purchase #6	$123.46	3.400%	$127.6576	$127.66	$127.65	$127.70
Purchase #7	$158.35	4.132%	$164.893	$164.89	$164.90	$164.90
7 purchase totals =	$1,121.71		$1,204.3901	$1,204.38	$1,204.40	$1,204.50