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	$147.50	3.270%	$152.3233	$152.32	$152.30	$152.30
Purchase #2	$54.96	10.550%	$60.7583	$60.76	$60.75	$60.80
Purchase #3	$106.85	4.660%	$111.8292	$111.83	$111.85	$111.80
Purchase #4	$113.38	8.601%	$123.1318	$123.13	$123.15	$123.10
Purchase #5	$92.37	9.410%	$101.062	$101.06	$101.05	$101.10
Purchase #6	$113.81	3.195%	$117.4462	$117.45	$117.45	$117.40
Purchase #7	$56.72	10.754%	$62.8197	$62.82	$62.80	$62.80
7 purchase totals =	$685.59		$729.3705	$729.37	$729.35	$729.30