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	$203.95	9.418%	$223.158	$223.16	$223.15	$223.20
Purchase #2	$189.30	3.698%	$196.3003	$196.30	$196.30	$196.30
Purchase #3	$5.69	10.296%	$6.2758	$6.28	$6.30	$6.30
Purchase #4	$58.72	4.523%	$61.3759	$61.38	$61.40	$61.40
Purchase #5	$138.69	5.709%	$146.6078	$146.61	$146.60	$146.60
Purchase #6	$113.72	5.112%	$119.5334	$119.53	$119.55	$119.50
Purchase #7	$34.25	8.127%	$37.0335	$37.03	$37.05	$37.00
7 purchase totals =	$744.32		$790.2847	$790.29	$790.35	$790.30