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	$106.51	12.523%	$119.8482	$119.85	$119.85	$119.80
Purchase #2	$75.33	10.710%	$83.3978	$83.40	$83.40	$83.40
Purchase #3	$110.50	5.109%	$116.1454	$116.15	$116.15	$116.10
Purchase #4	$66.89	10.654%	$74.0165	$74.02	$74.00	$74.00
Purchase #5	$79.41	5.159%	$83.5068	$83.51	$83.50	$83.50
Purchase #6	$93.77	12.847%	$105.8166	$105.82	$105.80	$105.80
Purchase #7	$165.82	8.469%	$179.8633	$179.86	$179.85	$179.90
7 purchase totals =	$698.23		$762.5946	$762.61	$762.55	$762.50