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	$14.63	3.825%	$15.1896	$15.19	$15.20	$15.20
Purchase #2	$56.90	6.737%	$60.7334	$60.73	$60.75	$60.70
Purchase #3	$82.33	9.233%	$89.9315	$89.93	$89.95	$89.90
Purchase #4	$163.98	4.691%	$171.6723	$171.67	$171.65	$171.70
Purchase #5	$143.90	6.242%	$152.8822	$152.88	$152.90	$152.90
Purchase #6	$215.72	4.382%	$225.1729	$225.17	$225.15	$225.20
Purchase #7	$217.30	7.465%	$233.5214	$233.52	$233.50	$233.50
7 purchase totals =	$894.76		$949.1033	$949.09	$949.10	$949.10