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	$210.92	7.779%	$227.3275	$227.33	$227.35	$227.30
Purchase #2	$154.66	11.450%	$172.3686	$172.37	$172.35	$172.40
Purchase #3	$241.29	3.709%	$250.2394	$250.24	$250.25	$250.20
Purchase #4	$128.27	9.848%	$140.902	$140.90	$140.90	$140.90
Purchase #5	$71.33	7.801%	$76.8945	$76.89	$76.90	$76.90
Purchase #6	$9.86	13.379%	$11.1792	$11.18	$11.20	$11.20
Purchase #7	$177.60	4.614%	$185.7945	$185.79	$185.80	$185.80
7 purchase totals =	$993.93		$1,064.7057	$1,064.70	$1,064.75	$1,064.70