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	$67.37	4.601%	$70.4697	$70.47	$70.45	$70.50
Purchase #2	$89.92	5.230%	$94.6228	$94.62	$94.60	$94.60
Purchase #3	$24.32	12.596%	$27.3833	$27.38	$27.40	$27.40
Purchase #4	$155.38	9.649%	$170.3726	$170.37	$170.35	$170.40
Purchase #5	$136.76	10.846%	$151.593	$151.59	$151.60	$151.60
Purchase #6	$19.85	10.117%	$21.8582	$21.86	$21.85	$21.90
Purchase #7	$213.61	3.749%	$221.6182	$221.62	$221.60	$221.60
7 purchase totals =	$707.21		$757.9178	$757.91	$757.85	$758.00