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	$95.82	9.548%	$104.9689	$104.97	$104.95	$105.00
Purchase #2	$40.73	3.327%	$42.0851	$42.09	$42.10	$42.10
Purchase #3	$119.76	4.811%	$125.5217	$125.52	$125.50	$125.50
Purchase #4	$101.59	10.195%	$111.9471	$111.95	$111.95	$111.90
Purchase #5	$180.74	4.853%	$189.5113	$189.51	$189.50	$189.50
Purchase #6	$120.67	11.506%	$134.5543	$134.55	$134.55	$134.60
Purchase #7	$229.73	8.440%	$249.1192	$249.12	$249.10	$249.10
7 purchase totals =	$889.04		$957.7076	$957.71	$957.65	$957.70