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	$204.87	8.630%	$222.5503	$222.55	$222.55	$222.60
Purchase #2	$100.87	8.480%	$109.4238	$109.42	$109.40	$109.40
Purchase #3	$123.86	10.662%	$137.066	$137.07	$137.05	$137.10
Purchase #4	$148.70	12.655%	$167.518	$167.52	$167.50	$167.50
Purchase #5	$195.93	4.363%	$204.4784	$204.48	$204.50	$204.50
Purchase #6	$21.87	10.442%	$24.1537	$24.15	$24.15	$24.20
Purchase #7	$18.97	4.458%	$19.8157	$19.82	$19.80	$19.80
7 purchase totals =	$815.07		$885.0059	$885.01	$884.95	$885.10