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	$95.59	5.442%	$100.792	$100.79	$100.80	$100.80
Purchase #2	$50.40	13.156%	$57.0306	$57.03	$57.05	$57.00
Purchase #3	$116.65	12.829%	$131.615	$131.62	$131.60	$131.60
Purchase #4	$30.60	8.393%	$33.1683	$33.17	$33.15	$33.20
Purchase #5	$222.85	12.142%	$249.9084	$249.91	$249.90	$249.90
Purchase #6	$121.39	9.200%	$132.5579	$132.56	$132.55	$132.60
Purchase #7	$38.98	8.516%	$42.2995	$42.30	$42.30	$42.30
7 purchase totals =	$676.46		$747.3717	$747.38	$747.35	$747.40