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	$73.53	8.421%	$79.722	$79.72	$79.70	$79.70
Purchase #2	$65.75	6.357%	$69.9297	$69.93	$69.95	$69.90
Purchase #3	$148.38	6.584%	$158.1493	$158.15	$158.15	$158.10
Purchase #4	$195.42	5.273%	$205.7245	$205.72	$205.70	$205.70
Purchase #5	$118.69	4.311%	$123.8067	$123.81	$123.80	$123.80
Purchase #6	$95.69	4.614%	$100.1051	$100.11	$100.10	$100.10
Purchase #7	$149.97	13.285%	$169.8935	$169.89	$169.90	$169.90
7 purchase totals =	$847.43		$907.3308	$907.33	$907.30	$907.20