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	$160.37	9.821%	$176.1199	$176.12	$176.10	$176.10
Purchase #2	$154.92	4.254%	$161.5103	$161.51	$161.50	$161.50
Purchase #3	$102.37	10.411%	$113.0277	$113.03	$113.05	$113.00
Purchase #4	$28.68	9.855%	$31.5064	$31.51	$31.50	$31.50
Purchase #5	$196.53	12.688%	$221.4657	$221.47	$221.45	$221.50
Purchase #6	$35.78	4.141%	$37.2616	$37.26	$37.25	$37.30
Purchase #7	$109.27	13.631%	$124.1646	$124.16	$124.15	$124.20
7 purchase totals =	$787.92		$865.0562	$865.06	$865.00	$865.10