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	$65.57	7.530%	$70.5074	$70.51	$70.50	$70.50
Purchase #2	$128.68	13.711%	$146.3233	$146.32	$146.30	$146.30
Purchase #3	$33.75	13.404%	$38.2739	$38.27	$38.25	$38.30
Purchase #4	$9.52	6.712%	$10.159	$10.16	$10.15	$10.20
Purchase #5	$146.38	6.872%	$156.4392	$156.44	$156.45	$156.40
Purchase #6	$60.27	3.625%	$62.4548	$62.45	$62.45	$62.50
Purchase #7	$193.43	10.592%	$213.9181	$213.92	$213.90	$213.90
7 purchase totals =	$637.60		$698.0757	$698.07	$698.00	$698.10