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	$94.68	4.692%	$99.1224	$99.12	$99.10	$99.10
Purchase #2	$41.76	12.715%	$47.0698	$47.07	$47.05	$47.10
Purchase #3	$207.58	5.559%	$219.1194	$219.12	$219.10	$219.10
Purchase #4	$80.54	12.398%	$90.5253	$90.53	$90.55	$90.50
Purchase #5	$84.30	11.627%	$94.1016	$94.10	$94.10	$94.10
Purchase #6	$66.28	5.630%	$70.0116	$70.01	$70.00	$70.00
Purchase #7	$56.93	13.682%	$64.7192	$64.72	$64.70	$64.70
7 purchase totals =	$632.07		$684.6693	$684.67	$684.60	$684.60