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	$98.97	7.442%	$106.3353	$106.34	$106.35	$106.30
Purchase #2	$103.60	5.201%	$108.9882	$108.99	$109.00	$109.00
Purchase #3	$24.32	7.697%	$26.1919	$26.19	$26.20	$26.20
Purchase #4	$101.86	7.594%	$109.5952	$109.60	$109.60	$109.60
Purchase #5	$100.47	11.141%	$111.6634	$111.66	$111.65	$111.70
Purchase #6	$31.45	7.560%	$33.8276	$33.83	$33.85	$33.80
Purchase #7	$158.76	8.126%	$171.6608	$171.66	$171.65	$171.70
7 purchase totals =	$619.43		$668.2624	$668.27	$668.30	$668.30