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	$90.91	4.680%	$95.1646	$95.16	$95.15	$95.20
Purchase #2	$76.39	11.381%	$85.0839	$85.08	$85.10	$85.10
Purchase #3	$56.54	10.240%	$62.3297	$62.33	$62.35	$62.30
Purchase #4	$31.27	7.444%	$33.5977	$33.60	$33.60	$33.60
Purchase #5	$147.32	4.430%	$153.8463	$153.85	$153.85	$153.80
Purchase #6	$59.28	3.372%	$61.2789	$61.28	$61.30	$61.30
Purchase #7	$233.64	7.784%	$251.8265	$251.83	$251.85	$251.80
7 purchase totals =	$695.35		$743.1276	$743.13	$743.20	$743.10