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	$196.91	6.592%	$209.8903	$209.89	$209.90	$209.90
Purchase #2	$119.43	12.494%	$134.3516	$134.35	$134.35	$134.40
Purchase #3	$78.83	9.310%	$86.1691	$86.17	$86.15	$86.20
Purchase #4	$14.32	4.158%	$14.9154	$14.92	$14.90	$14.90
Purchase #5	$91.79	8.359%	$99.4627	$99.46	$99.45	$99.50
Purchase #6	$19.32	7.357%	$20.7414	$20.74	$20.75	$20.70
Purchase #7	$164.37	5.265%	$173.0241	$173.02	$173.00	$173.00
7 purchase totals =	$684.97		$738.5546	$738.55	$738.50	$738.60