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	$67.73	4.247%	$70.6065	$70.61	$70.60	$70.60
Purchase #2	$156.31	6.497%	$166.4655	$166.47	$166.45	$166.50
Purchase #3	$176.91	13.296%	$200.432	$200.43	$200.45	$200.40
Purchase #4	$21.84	13.455%	$24.7786	$24.78	$24.80	$24.80
Purchase #5	$146.51	5.155%	$154.0626	$154.06	$154.05	$154.10
Purchase #6	$80.84	6.233%	$85.8788	$85.88	$85.90	$85.90
Purchase #7	$38.84	5.845%	$41.1102	$41.11	$41.10	$41.10
7 purchase totals =	$688.98		$743.3342	$743.34	$743.35	$743.40