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	$34.41	10.182%	$37.9136	$37.91	$37.90	$37.90
Purchase #2	$110.98	3.574%	$114.9464	$114.95	$114.95	$114.90
Purchase #3	$27.61	6.748%	$29.4731	$29.47	$29.45	$29.50
Purchase #4	$71.94	7.246%	$77.1528	$77.15	$77.15	$77.20
Purchase #5	$65.88	12.269%	$73.9628	$73.96	$73.95	$74.00
Purchase #6	$54.41	9.796%	$59.74	$59.74	$59.75	$59.70
Purchase #7	$11.98	7.597%	$12.8901	$12.89	$12.90	$12.90
7 purchase totals =	$377.21		$406.0788	$406.07	$406.05	$406.10