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	$178.74	10.135%	$196.8553	$196.86	$196.85	$196.90
Purchase #2	$109.71	12.184%	$123.0771	$123.08	$123.10	$123.10
Purchase #3	$64.84	4.670%	$67.868	$67.87	$67.85	$67.90
Purchase #4	$33.83	13.823%	$38.5063	$38.51	$38.50	$38.50
Purchase #5	$242.68	7.481%	$260.8349	$260.83	$260.85	$260.80
Purchase #6	$29.78	9.568%	$32.6294	$32.63	$32.65	$32.60
Purchase #7	$76.37	9.175%	$83.3769	$83.38	$83.40	$83.40
7 purchase totals =	$735.95		$803.1479	$803.16	$803.20	$803.20