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	$123.83	7.113%	$132.638	$132.64	$132.65	$132.60
Purchase #2	$52.90	8.778%	$57.5436	$57.54	$57.55	$57.50
Purchase #3	$90.72	9.242%	$99.1043	$99.10	$99.10	$99.10
Purchase #4	$78.41	13.277%	$88.8205	$88.82	$88.80	$88.80
Purchase #5	$13.77	11.312%	$15.3277	$15.33	$15.35	$15.30
Purchase #6	$74.96	3.338%	$77.4622	$77.46	$77.45	$77.50
Purchase #7	$97.40	5.598%	$102.8525	$102.85	$102.85	$102.90
7 purchase totals =	$531.99		$573.7488	$573.74	$573.75	$573.70