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	$83.90	7.671%	$90.336	$90.34	$90.35	$90.30
Purchase #2	$93.90	7.409%	$100.8571	$100.86	$100.85	$100.90
Purchase #3	$113.59	8.374%	$123.102	$123.10	$123.10	$123.10
Purchase #4	$30.32	3.264%	$31.3096	$31.31	$31.30	$31.30
Purchase #5	$158.62	8.688%	$172.4009	$172.40	$172.40	$172.40
Purchase #6	$125.34	7.662%	$134.9436	$134.94	$134.95	$134.90
Purchase #7	$150.36	13.300%	$170.3579	$170.36	$170.35	$170.40
7 purchase totals =	$756.03		$823.3071	$823.31	$823.30	$823.30