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	$201.89	11.581%	$225.2709	$225.27	$225.25	$225.30
Purchase #2	$221.81	10.341%	$244.7474	$244.75	$244.75	$244.70
Purchase #3	$136.94	11.667%	$152.9168	$152.92	$152.90	$152.90
Purchase #4	$18.76	12.671%	$21.1371	$21.14	$21.15	$21.10
Purchase #5	$243.42	13.627%	$276.5908	$276.59	$276.60	$276.60
Purchase #6	$117.59	11.607%	$131.2387	$131.24	$131.25	$131.20
Purchase #7	$106.87	8.260%	$115.6975	$115.70	$115.70	$115.70
7 purchase totals =	$1,047.28		$1,167.5992	$1,167.61	$1,167.60	$1,167.50