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	$172.72	5.645%	$182.47	$182.47	$182.45	$182.50
Purchase #2	$40.96	13.461%	$46.4736	$46.47	$46.45	$46.50
Purchase #3	$209.46	5.634%	$221.261	$221.26	$221.25	$221.30
Purchase #4	$150.55	12.307%	$169.0782	$169.08	$169.10	$169.10
Purchase #5	$81.47	11.634%	$90.9482	$90.95	$90.95	$90.90
Purchase #6	$20.83	4.274%	$21.7203	$21.72	$21.70	$21.70
Purchase #7	$14.25	5.539%	$15.0393	$15.04	$15.05	$15.00
7 purchase totals =	$690.24		$746.9906	$746.99	$746.95	$747.00