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	$234.35	11.719%	$261.8135	$261.81	$261.80	$261.80
Purchase #2	$91.66	12.777%	$103.3714	$103.37	$103.35	$103.40
Purchase #3	$14.39	4.383%	$15.0207	$15.02	$15.00	$15.00
Purchase #4	$70.56	11.771%	$78.8656	$78.87	$78.85	$78.90
Purchase #5	$228.65	6.638%	$243.8278	$243.83	$243.85	$243.80
Purchase #6	$148.42	12.172%	$166.4857	$166.49	$166.50	$166.50
Purchase #7	$180.77	13.681%	$205.5011	$205.50	$205.50	$205.50
7 purchase totals =	$968.80		$1,074.8858	$1,074.89	$1,074.85	$1,074.90