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	$116.85	13.356%	$132.4565	$132.46	$132.45	$132.50
Purchase #2	$95.25	5.110%	$100.1173	$100.12	$100.10	$100.10
Purchase #3	$228.78	11.419%	$254.9044	$254.90	$254.90	$254.90
Purchase #4	$91.61	7.128%	$98.14	$98.14	$98.15	$98.10
Purchase #5	$68.78	12.169%	$77.1498	$77.15	$77.15	$77.10
Purchase #6	$133.89	3.131%	$138.0821	$138.08	$138.10	$138.10
Purchase #7	$238.31	12.692%	$268.5563	$268.56	$268.55	$268.60
7 purchase totals =	$973.47		$1,069.4064	$1,069.41	$1,069.40	$1,069.40