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	$25.66	8.450%	$27.8283	$27.83	$27.85	$27.80
Purchase #2	$191.58	4.656%	$200.5	$200.50	$200.50	$200.50
Purchase #3	$151.71	5.277%	$159.7157	$159.72	$159.70	$159.70
Purchase #4	$54.81	9.291%	$59.9024	$59.90	$59.90	$59.90
Purchase #5	$182.50	11.126%	$202.805	$202.81	$202.80	$202.80
Purchase #6	$65.65	10.601%	$72.6096	$72.61	$72.60	$72.60
Purchase #7	$192.26	4.190%	$200.3157	$200.32	$200.30	$200.30
7 purchase totals =	$864.17		$923.6767	$923.69	$923.65	$923.60