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	$44.99	7.696%	$48.4524	$48.45	$48.45	$48.50
Purchase #2	$61.85	8.848%	$67.3225	$67.32	$67.30	$67.30
Purchase #3	$80.55	10.856%	$89.2945	$89.29	$89.30	$89.30
Purchase #4	$75.43	7.380%	$80.9967	$81.00	$81.00	$81.00
Purchase #5	$142.79	6.168%	$151.5973	$151.60	$151.60	$151.60
Purchase #6	$79.93	7.595%	$86.0007	$86.00	$86.00	$86.00
Purchase #7	$181.57	10.625%	$200.8618	$200.86	$200.85	$200.90
7 purchase totals =	$667.11		$724.5259	$724.52	$724.50	$724.60