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	$131.35	6.657%	$140.094	$140.09	$140.10	$140.10
Purchase #2	$83.28	3.795%	$86.4405	$86.44	$86.45	$86.40
Purchase #3	$133.98	9.363%	$146.5245	$146.52	$146.50	$146.50
Purchase #4	$174.52	5.178%	$183.5566	$183.56	$183.55	$183.60
Purchase #5	$32.67	13.460%	$37.0674	$37.07	$37.05	$37.10
Purchase #6	$20.91	4.808%	$21.9154	$21.92	$21.90	$21.90
Purchase #7	$194.90	3.107%	$200.9555	$200.96	$200.95	$201.00
7 purchase totals =	$771.61		$816.5539	$816.56	$816.50	$816.60