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	$80.37	13.696%	$91.3775	$91.38	$91.40	$91.40
Purchase #2	$106.60	6.484%	$113.5119	$113.51	$113.50	$113.50
Purchase #3	$241.30	7.148%	$258.5481	$258.55	$258.55	$258.50
Purchase #4	$20.87	13.147%	$23.6138	$23.61	$23.60	$23.60
Purchase #5	$171.87	6.746%	$183.4644	$183.46	$183.45	$183.50
Purchase #6	$233.85	3.277%	$241.5133	$241.51	$241.50	$241.50
Purchase #7	$247.78	3.543%	$256.5588	$256.56	$256.55	$256.60
7 purchase totals =	$1,102.64		$1,168.5878	$1,168.58	$1,168.55	$1,168.60