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	$135.43	7.296%	$145.311	$145.31	$145.30	$145.30
Purchase #2	$95.55	8.555%	$103.7243	$103.72	$103.70	$103.70
Purchase #3	$106.42	3.287%	$109.918	$109.92	$109.90	$109.90
Purchase #4	$127.74	12.223%	$143.3537	$143.35	$143.35	$143.40
Purchase #5	$94.51	5.269%	$99.4897	$99.49	$99.50	$99.50
Purchase #6	$116.52	3.485%	$120.5807	$120.58	$120.60	$120.60
Purchase #7	$30.99	12.812%	$34.9604	$34.96	$34.95	$35.00
7 purchase totals =	$707.16		$757.3378	$757.33	$757.30	$757.40