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	$147.75	4.386%	$154.2303	$154.23	$154.25	$154.20
Purchase #2	$173.29	6.704%	$184.9074	$184.91	$184.90	$184.90
Purchase #3	$167.93	5.298%	$176.8269	$176.83	$176.85	$176.80
Purchase #4	$139.70	9.167%	$152.5063	$152.51	$152.50	$152.50
Purchase #5	$61.38	5.670%	$64.8602	$64.86	$64.85	$64.90
Purchase #6	$9.98	13.764%	$11.3536	$11.35	$11.35	$11.40
Purchase #7	$148.52	12.843%	$167.5944	$167.59	$167.60	$167.60
7 purchase totals =	$848.55		$912.2791	$912.28	$912.30	$912.30