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	$170.77	9.420%	$186.8565	$186.86	$186.85	$186.90
Purchase #2	$184.92	3.208%	$190.8522	$190.85	$190.85	$190.90
Purchase #3	$201.86	10.683%	$223.4247	$223.42	$223.40	$223.40
Purchase #4	$166.48	5.191%	$175.122	$175.12	$175.10	$175.10
Purchase #5	$10.83	3.816%	$11.2433	$11.24	$11.25	$11.20
Purchase #6	$166.71	13.158%	$188.6457	$188.65	$188.65	$188.60
Purchase #7	$63.66	10.704%	$70.4742	$70.47	$70.45	$70.50
7 purchase totals =	$965.23		$1,046.6186	$1,046.61	$1,046.55	$1,046.60