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	$143.85	3.461%	$148.8286	$148.83	$148.85	$148.80
Purchase #2	$211.30	3.178%	$218.0151	$218.02	$218.00	$218.00
Purchase #3	$52.86	11.792%	$59.0933	$59.09	$59.10	$59.10
Purchase #4	$19.48	5.736%	$20.5974	$20.60	$20.60	$20.60
Purchase #5	$160.62	13.672%	$182.58	$182.58	$182.60	$182.60
Purchase #6	$103.42	6.725%	$110.375	$110.38	$110.40	$110.40
Purchase #7	$181.97	13.107%	$205.8208	$205.82	$205.80	$205.80
7 purchase totals =	$873.50		$945.3102	$945.32	$945.35	$945.30