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	$82.91	3.523%	$85.8309	$85.83	$85.85	$85.80
Purchase #2	$61.97	13.678%	$70.4463	$70.45	$70.45	$70.40
Purchase #3	$150.55	11.151%	$167.3378	$167.34	$167.35	$167.30
Purchase #4	$62.25	11.765%	$69.5737	$69.57	$69.55	$69.60
Purchase #5	$221.77	5.357%	$233.6502	$233.65	$233.65	$233.70
Purchase #6	$175.80	13.320%	$199.2166	$199.22	$199.20	$199.20
Purchase #7	$145.29	7.726%	$156.5151	$156.52	$156.50	$156.50
7 purchase totals =	$900.54		$982.5706	$982.58	$982.55	$982.50