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	$105.86	11.733%	$118.2806	$118.28	$118.30	$118.30
Purchase #2	$163.37	13.365%	$185.2044	$185.20	$185.20	$185.20
Purchase #3	$47.39	6.297%	$50.3741	$50.37	$50.35	$50.40
Purchase #4	$190.40	4.132%	$198.2673	$198.27	$198.25	$198.30
Purchase #5	$166.32	13.711%	$189.1241	$189.12	$189.10	$189.10
Purchase #6	$179.62	4.735%	$188.125	$188.13	$188.15	$188.10
Purchase #7	$146.93	6.591%	$156.6142	$156.61	$156.60	$156.60
7 purchase totals =	$999.89		$1,085.9897	$1,085.98	$1,085.95	$1,086.00