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	$145.78	11.551%	$162.619	$162.62	$162.60	$162.60
Purchase #2	$244.47	10.632%	$270.4621	$270.46	$270.45	$270.50
Purchase #3	$42.85	3.738%	$44.4517	$44.45	$44.45	$44.50
Purchase #4	$179.82	3.273%	$185.7055	$185.71	$185.70	$185.70
Purchase #5	$34.44	13.472%	$39.0798	$39.08	$39.10	$39.10
Purchase #6	$237.97	11.797%	$266.0433	$266.04	$266.05	$266.00
Purchase #7	$146.36	13.292%	$165.8142	$165.81	$165.80	$165.80
7 purchase totals =	$1,031.69		$1,134.1756	$1,134.17	$1,134.15	$1,134.20