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	$103.45	10.247%	$114.0505	$114.05	$114.05	$114.10
Purchase #2	$176.38	3.707%	$182.9184	$182.92	$182.90	$182.90
Purchase #3	$240.64	6.195%	$255.5476	$255.55	$255.55	$255.50
Purchase #4	$83.66	7.240%	$89.717	$89.72	$89.70	$89.70
Purchase #5	$36.61	5.532%	$38.6353	$38.64	$38.65	$38.60
Purchase #6	$177.52	4.544%	$185.5865	$185.59	$185.60	$185.60
Purchase #7	$99.60	10.490%	$110.048	$110.05	$110.05	$110.00
7 purchase totals =	$917.86		$976.5033	$976.52	$976.50	$976.40