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	$226.42	13.288%	$256.5067	$256.51	$256.50	$256.50
Purchase #2	$237.50	7.627%	$255.6141	$255.61	$255.60	$255.60
Purchase #3	$212.99	4.762%	$223.1326	$223.13	$223.15	$223.10
Purchase #4	$31.90	8.109%	$34.4868	$34.49	$34.50	$34.50
Purchase #5	$185.88	13.665%	$211.2805	$211.28	$211.30	$211.30
Purchase #6	$93.60	4.308%	$97.6323	$97.63	$97.65	$97.60
Purchase #7	$72.53	7.644%	$78.0742	$78.07	$78.05	$78.10
7 purchase totals =	$1,060.82		$1,156.7272	$1,156.72	$1,156.75	$1,156.70