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	$223.32	8.772%	$242.9096	$242.91	$242.90	$242.90
Purchase #2	$72.83	10.823%	$80.7124	$80.71	$80.70	$80.70
Purchase #3	$76.74	7.152%	$82.2284	$82.23	$82.25	$82.20
Purchase #4	$187.59	11.521%	$209.2022	$209.20	$209.20	$209.20
Purchase #5	$95.83	8.432%	$103.9104	$103.91	$103.90	$103.90
Purchase #6	$222.78	6.519%	$237.303	$237.30	$237.30	$237.30
Purchase #7	$110.62	8.177%	$119.6654	$119.67	$119.65	$119.70
7 purchase totals =	$989.71		$1,075.9314	$1,075.93	$1,075.90	$1,075.90