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	$150.44	10.499%	$166.2347	$166.23	$166.25	$166.20
Purchase #2	$28.48	10.591%	$31.4963	$31.50	$31.50	$31.50
Purchase #3	$146.96	3.236%	$151.7156	$151.72	$151.70	$151.70
Purchase #4	$199.73	9.816%	$219.3355	$219.34	$219.35	$219.30
Purchase #5	$51.75	4.504%	$54.0808	$54.08	$54.10	$54.10
Purchase #6	$112.45	12.582%	$126.5985	$126.60	$126.60	$126.60
Purchase #7	$166.58	13.231%	$188.6202	$188.62	$188.60	$188.60
7 purchase totals =	$856.39		$938.0816	$938.09	$938.10	$938.00