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	$60.83	8.270%	$65.8606	$65.86	$65.85	$65.90
Purchase #2	$76.42	12.815%	$86.2132	$86.21	$86.20	$86.20
Purchase #3	$41.44	5.156%	$43.5766	$43.58	$43.60	$43.60
Purchase #4	$90.33	6.791%	$96.4643	$96.46	$96.45	$96.50
Purchase #5	$13.95	4.158%	$14.53	$14.53	$14.55	$14.50
Purchase #6	$124.45	13.800%	$141.6241	$141.62	$141.60	$141.60
Purchase #7	$16.68	12.637%	$18.7879	$18.79	$18.80	$18.80
7 purchase totals =	$424.10		$467.0567	$467.05	$467.05	$467.10