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	$66.61	8.762%	$72.4464	$72.45	$72.45	$72.40
Purchase #2	$66.42	12.323%	$74.6049	$74.60	$74.60	$74.60
Purchase #3	$206.79	7.323%	$221.9332	$221.93	$221.95	$221.90
Purchase #4	$224.83	11.822%	$251.4094	$251.41	$251.40	$251.40
Purchase #5	$183.81	13.588%	$208.7861	$208.79	$208.80	$208.80
Purchase #6	$171.61	10.695%	$189.9637	$189.96	$189.95	$190.00
Purchase #7	$85.85	4.410%	$89.636	$89.64	$89.65	$89.60
7 purchase totals =	$1,005.92		$1,108.7797	$1,108.78	$1,108.80	$1,108.70