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	$54.25	11.333%	$60.3982	$60.40	$60.40	$60.40
Purchase #2	$160.39	4.275%	$167.2467	$167.25	$167.25	$167.20
Purchase #3	$32.75	10.206%	$36.0925	$36.09	$36.10	$36.10
Purchase #4	$244.61	12.662%	$275.5825	$275.58	$275.60	$275.60
Purchase #5	$149.27	12.696%	$168.2213	$168.22	$168.20	$168.20
Purchase #6	$40.78	6.263%	$43.3341	$43.33	$43.35	$43.30
Purchase #7	$166.85	7.385%	$179.1719	$179.17	$179.15	$179.20
7 purchase totals =	$848.90		$930.0472	$930.04	$930.05	$930.00