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	$90.33	5.523%	$95.3189	$95.32	$95.30	$95.30
Purchase #2	$244.92	11.700%	$273.5756	$273.58	$273.60	$273.60
Purchase #3	$202.57	4.428%	$211.5398	$211.54	$211.55	$211.50
Purchase #4	$244.53	3.499%	$253.0861	$253.09	$253.10	$253.10
Purchase #5	$127.99	7.762%	$137.9246	$137.92	$137.90	$137.90
Purchase #6	$105.87	10.314%	$116.7894	$116.79	$116.80	$116.80
Purchase #7	$100.48	7.480%	$107.9959	$108.00	$108.00	$108.00
7 purchase totals =	$1,116.69		$1,196.2303	$1,196.24	$1,196.25	$1,196.20