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	$237.95	7.783%	$256.4696	$256.47	$256.45	$256.50
Purchase #2	$13.38	6.509%	$14.2509	$14.25	$14.25	$14.30
Purchase #3	$105.37	13.401%	$119.4906	$119.49	$119.50	$119.50
Purchase #4	$7.34	5.114%	$7.7154	$7.72	$7.70	$7.70
Purchase #5	$96.93	13.270%	$109.7926	$109.79	$109.80	$109.80
Purchase #6	$16.69	9.530%	$18.2806	$18.28	$18.30	$18.30
Purchase #7	$72.96	6.729%	$77.8695	$77.87	$77.85	$77.90
7 purchase totals =	$550.62		$603.8692	$603.87	$603.85	$604.00