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	$59.49	12.123%	$66.702	$66.70	$66.70	$66.70
Purchase #2	$12.82	5.814%	$13.5654	$13.57	$13.55	$13.60
Purchase #3	$139.87	13.376%	$158.579	$158.58	$158.60	$158.60
Purchase #4	$183.96	5.221%	$193.5646	$193.56	$193.55	$193.60
Purchase #5	$250.93	12.312%	$281.8245	$281.82	$281.80	$281.80
Purchase #6	$206.64	6.322%	$219.7038	$219.70	$219.70	$219.70
Purchase #7	$82.58	8.382%	$89.5019	$89.50	$89.50	$89.50
7 purchase totals =	$936.29		$1,023.4412	$1,023.43	$1,023.40	$1,023.50