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	$145.79	11.263%	$162.2103	$162.21	$162.20	$162.20
Purchase #2	$150.35	5.443%	$158.5336	$158.53	$158.55	$158.50
Purchase #3	$91.73	10.536%	$101.3947	$101.39	$101.40	$101.40
Purchase #4	$138.40	13.125%	$156.565	$156.57	$156.55	$156.60
Purchase #5	$41.78	8.451%	$45.3108	$45.31	$45.30	$45.30
Purchase #6	$151.54	5.206%	$159.4292	$159.43	$159.45	$159.40
Purchase #7	$231.99	7.407%	$249.1735	$249.17	$249.15	$249.20
7 purchase totals =	$951.58		$1,032.6171	$1,032.61	$1,032.60	$1,032.60