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	$91.96	9.491%	$100.6879	$100.69	$100.70	$100.70
Purchase #2	$96.45	9.741%	$105.8452	$105.85	$105.85	$105.80
Purchase #3	$109.71	8.610%	$119.156	$119.16	$119.15	$119.20
Purchase #4	$178.60	4.164%	$186.0369	$186.04	$186.05	$186.00
Purchase #5	$109.99	10.681%	$121.738	$121.74	$121.75	$121.70
Purchase #6	$161.83	6.592%	$172.4978	$172.50	$172.50	$172.50
Purchase #7	$201.68	4.480%	$210.7153	$210.72	$210.70	$210.70
7 purchase totals =	$950.22		$1,016.6771	$1,016.70	$1,016.70	$1,016.60