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	$184.85	11.218%	$205.5865	$205.59	$205.60	$205.60
Purchase #2	$148.42	12.847%	$167.4875	$167.49	$167.50	$167.50
Purchase #3	$83.36	13.165%	$94.3343	$94.33	$94.35	$94.30
Purchase #4	$245.79	4.745%	$257.4527	$257.45	$257.45	$257.50
Purchase #5	$53.60	12.527%	$60.3145	$60.31	$60.30	$60.30
Purchase #6	$244.65	12.812%	$275.9946	$275.99	$276.00	$276.00
Purchase #7	$82.59	9.229%	$90.2122	$90.21	$90.20	$90.20
7 purchase totals =	$1,043.26		$1,151.3823	$1,151.37	$1,151.40	$1,151.40