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	$149.63	12.619%	$168.5118	$168.51	$168.50	$168.50
Purchase #2	$53.56	11.778%	$59.8683	$59.87	$59.85	$59.90
Purchase #3	$119.89	6.109%	$127.2141	$127.21	$127.20	$127.20
Purchase #4	$143.95	12.140%	$161.4255	$161.43	$161.45	$161.40
Purchase #5	$82.55	5.552%	$87.1332	$87.13	$87.15	$87.10
Purchase #6	$180.53	7.547%	$194.1546	$194.15	$194.15	$194.20
Purchase #7	$61.27	4.487%	$64.0192	$64.02	$64.00	$64.00
7 purchase totals =	$791.38		$862.3267	$862.32	$862.30	$862.30