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	$38.28	7.857%	$41.2877	$41.29	$41.30	$41.30
Purchase #2	$7.90	4.479%	$8.2538	$8.25	$8.25	$8.30
Purchase #3	$144.76	7.347%	$155.3955	$155.40	$155.40	$155.40
Purchase #4	$117.64	11.151%	$130.758	$130.76	$130.75	$130.80
Purchase #5	$101.87	9.833%	$111.8869	$111.89	$111.90	$111.90
Purchase #6	$81.41	13.506%	$92.4052	$92.41	$92.40	$92.40
Purchase #7	$114.59	3.723%	$118.8562	$118.86	$118.85	$118.90
7 purchase totals =	$606.45		$658.8433	$658.86	$658.85	$659.00