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	$104.47	7.428%	$112.23	$112.23	$112.25	$112.20
Purchase #2	$100.37	3.300%	$103.6822	$103.68	$103.70	$103.70
Purchase #3	$146.63	3.109%	$151.1887	$151.19	$151.20	$151.20
Purchase #4	$228.26	9.142%	$249.1275	$249.13	$249.15	$249.10
Purchase #5	$196.91	9.405%	$215.4294	$215.43	$215.45	$215.40
Purchase #6	$114.97	13.331%	$130.2967	$130.30	$130.30	$130.30
Purchase #7	$139.32	8.778%	$151.5495	$151.55	$151.55	$151.50
7 purchase totals =	$1,030.93		$1,113.5040	$1,113.51	$1,113.60	$1,113.40