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	$142.78	3.228%	$147.3889	$147.39	$147.40	$147.40
Purchase #2	$75.60	9.201%	$82.556	$82.56	$82.55	$82.60
Purchase #3	$144.33	12.506%	$162.3799	$162.38	$162.40	$162.40
Purchase #4	$199.66	8.607%	$216.8447	$216.84	$216.85	$216.80
Purchase #5	$234.90	13.444%	$266.48	$266.48	$266.50	$266.50
Purchase #6	$87.85	9.191%	$95.9243	$95.92	$95.90	$95.90
Purchase #7	$93.82	3.848%	$97.4302	$97.43	$97.45	$97.40
7 purchase totals =	$978.94		$1,069.0040	$1,069.00	$1,069.05	$1,069.00