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	$109.93	5.739%	$116.2389	$116.24	$116.25	$116.20
Purchase #2	$22.96	11.362%	$25.5687	$25.57	$25.55	$25.60
Purchase #3	$134.54	12.507%	$151.3669	$151.37	$151.35	$151.40
Purchase #4	$72.89	9.272%	$79.6484	$79.65	$79.65	$79.60
Purchase #5	$19.25	9.731%	$21.1232	$21.12	$21.10	$21.10
Purchase #6	$206.54	7.587%	$222.2102	$222.21	$222.20	$222.20
Purchase #7	$142.39	4.255%	$148.4487	$148.45	$148.45	$148.40
7 purchase totals =	$708.50		$764.6050	$764.61	$764.55	$764.50