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	$186.89	7.219%	$200.3816	$200.38	$200.40	$200.40
Purchase #2	$8.52	11.703%	$9.5171	$9.52	$9.50	$9.50
Purchase #3	$98.50	5.337%	$103.7569	$103.76	$103.75	$103.80
Purchase #4	$176.99	8.401%	$191.8589	$191.86	$191.85	$191.90
Purchase #5	$11.88	10.634%	$13.1433	$13.14	$13.15	$13.10
Purchase #6	$28.89	10.103%	$31.8088	$31.81	$31.80	$31.80
Purchase #7	$197.56	5.695%	$208.811	$208.81	$208.80	$208.80
7 purchase totals =	$709.23		$759.2776	$759.28	$759.25	$759.30