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	$120.71	11.794%	$134.9465	$134.95	$134.95	$134.90
Purchase #2	$123.72	6.286%	$131.497	$131.50	$131.50	$131.50
Purchase #3	$109.80	13.645%	$124.7822	$124.78	$124.80	$124.80
Purchase #4	$98.78	5.602%	$104.3137	$104.31	$104.30	$104.30
Purchase #5	$220.29	12.831%	$248.5554	$248.56	$248.55	$248.60
Purchase #6	$50.48	6.169%	$53.5941	$53.59	$53.60	$53.60
Purchase #7	$141.30	5.828%	$149.535	$149.54	$149.55	$149.50
7 purchase totals =	$865.08		$947.2239	$947.23	$947.25	$947.20