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	$50.98	5.163%	$53.6121	$53.61	$53.60	$53.60
Purchase #2	$239.50	11.578%	$267.2293	$267.23	$267.25	$267.20
Purchase #3	$39.66	5.580%	$41.873	$41.87	$41.85	$41.90
Purchase #4	$168.32	13.415%	$190.9001	$190.90	$190.90	$190.90
Purchase #5	$22.83	4.262%	$23.803	$23.80	$23.80	$23.80
Purchase #6	$128.66	11.599%	$143.5833	$143.58	$143.60	$143.60
Purchase #7	$169.80	10.324%	$187.3302	$187.33	$187.35	$187.30
7 purchase totals =	$819.75		$908.3310	$908.32	$908.35	$908.30