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	$96.54	4.244%	$100.6372	$100.64	$100.65	$100.60
Purchase #2	$115.48	10.255%	$127.3225	$127.32	$127.30	$127.30
Purchase #3	$183.69	10.252%	$202.5219	$202.52	$202.50	$202.50
Purchase #4	$64.49	11.685%	$72.0257	$72.03	$72.05	$72.00
Purchase #5	$46.89	6.394%	$49.8881	$49.89	$49.90	$49.90
Purchase #6	$216.63	8.702%	$235.4811	$235.48	$235.50	$235.50
Purchase #7	$25.47	12.323%	$28.6087	$28.61	$28.60	$28.60
7 purchase totals =	$749.19		$816.4852	$816.49	$816.50	$816.40