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	$189.49	11.511%	$211.3022	$211.30	$211.30	$211.30
Purchase #2	$106.53	4.707%	$111.5444	$111.54	$111.55	$111.50
Purchase #3	$85.41	10.522%	$94.3968	$94.40	$94.40	$94.40
Purchase #4	$75.50	13.563%	$85.7401	$85.74	$85.75	$85.70
Purchase #5	$126.33	13.335%	$143.1761	$143.18	$143.20	$143.20
Purchase #6	$31.75	6.643%	$33.8592	$33.86	$33.85	$33.90
Purchase #7	$24.96	11.578%	$27.8499	$27.85	$27.85	$27.80
7 purchase totals =	$639.97		$707.8687	$707.87	$707.90	$707.80