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	$117.69	7.727%	$126.7839	$126.78	$126.80	$126.80
Purchase #2	$36.81	4.407%	$38.4322	$38.43	$38.45	$38.40
Purchase #3	$44.98	10.702%	$49.7938	$49.79	$49.80	$49.80
Purchase #4	$211.41	8.411%	$229.1917	$229.19	$229.20	$229.20
Purchase #5	$78.29	10.601%	$86.5895	$86.59	$86.60	$86.60
Purchase #6	$157.46	10.389%	$173.8185	$173.82	$173.80	$173.80
Purchase #7	$81.38	11.268%	$90.5499	$90.55	$90.55	$90.50
7 purchase totals =	$728.02		$795.1595	$795.15	$795.20	$795.10