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	$22.65	8.551%	$24.5868	$24.59	$24.60	$24.60
Purchase #2	$140.85	8.150%	$152.3293	$152.33	$152.35	$152.30
Purchase #3	$236.25	9.437%	$258.5449	$258.54	$258.55	$258.50
Purchase #4	$137.89	10.476%	$152.3354	$152.34	$152.35	$152.30
Purchase #5	$22.85	4.700%	$23.924	$23.92	$23.90	$23.90
Purchase #6	$190.66	5.214%	$200.601	$200.60	$200.60	$200.60
Purchase #7	$219.92	8.426%	$238.4505	$238.45	$238.45	$238.50
7 purchase totals =	$971.07		$1,050.7719	$1,050.77	$1,050.80	$1,050.70