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	$229.58	11.764%	$256.5878	$256.59	$256.60	$256.60
Purchase #2	$166.84	7.683%	$179.6583	$179.66	$179.65	$179.70
Purchase #3	$65.63	10.443%	$72.4837	$72.48	$72.50	$72.50
Purchase #4	$126.64	7.460%	$136.0873	$136.09	$136.10	$136.10
Purchase #5	$155.48	3.375%	$160.7275	$160.73	$160.75	$160.70
Purchase #6	$31.34	3.543%	$32.4504	$32.45	$32.45	$32.50
Purchase #7	$204.83	12.790%	$231.0278	$231.03	$231.05	$231.00
7 purchase totals =	$980.34		$1,069.0228	$1,069.03	$1,069.10	$1,069.10