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	$54.47	11.643%	$60.8119	$60.81	$60.80	$60.80
Purchase #2	$138.56	7.198%	$148.5335	$148.53	$148.55	$148.50
Purchase #3	$151.46	10.508%	$167.3754	$167.38	$167.40	$167.40
Purchase #4	$202.49	12.841%	$228.4917	$228.49	$228.50	$228.50
Purchase #5	$96.85	8.371%	$104.9573	$104.96	$104.95	$105.00
Purchase #6	$233.52	3.837%	$242.4802	$242.48	$242.50	$242.50
Purchase #7	$67.52	4.554%	$70.5949	$70.59	$70.60	$70.60
7 purchase totals =	$944.87		$1,023.2449	$1,023.24	$1,023.30	$1,023.30