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	$57.94	5.860%	$61.3353	$61.34	$61.35	$61.30
Purchase #2	$129.85	6.590%	$138.4071	$138.41	$138.40	$138.40
Purchase #3	$44.39	4.304%	$46.3005	$46.30	$46.30	$46.30
Purchase #4	$169.71	8.340%	$183.8638	$183.86	$183.85	$183.90
Purchase #5	$54.86	12.447%	$61.6884	$61.69	$61.70	$61.70
Purchase #6	$249.50	5.769%	$263.8937	$263.89	$263.90	$263.90
Purchase #7	$151.82	13.689%	$172.6026	$172.60	$172.60	$172.60
7 purchase totals =	$858.07		$928.0914	$928.09	$928.10	$928.10