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	$55.78	10.652%	$61.7217	$61.72	$61.70	$61.70
Purchase #2	$162.56	12.608%	$183.0556	$183.06	$183.05	$183.10
Purchase #3	$36.65	3.599%	$37.969	$37.97	$37.95	$38.00
Purchase #4	$55.39	11.670%	$61.854	$61.85	$61.85	$61.90
Purchase #5	$40.45	4.155%	$42.1307	$42.13	$42.15	$42.10
Purchase #6	$69.86	7.677%	$75.2232	$75.22	$75.20	$75.20
Purchase #7	$129.82	7.142%	$139.0917	$139.09	$139.10	$139.10
7 purchase totals =	$550.51		$601.0459	$601.04	$601.00	$601.10