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	$222.97	7.782%	$240.3215	$240.32	$240.30	$240.30
Purchase #2	$59.76	3.781%	$62.0195	$62.02	$62.00	$62.00
Purchase #3	$213.44	13.658%	$242.5916	$242.59	$242.60	$242.60
Purchase #4	$73.71	11.770%	$82.3857	$82.39	$82.40	$82.40
Purchase #5	$220.88	12.648%	$248.8169	$248.82	$248.80	$248.80
Purchase #6	$61.90	10.748%	$68.553	$68.55	$68.55	$68.60
Purchase #7	$63.40	10.719%	$70.1958	$70.20	$70.20	$70.20
7 purchase totals =	$916.06		$1,014.8840	$1,014.89	$1,014.85	$1,014.90