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	$14.37	10.505%	$15.8796	$15.88	$15.90	$15.90
Purchase #2	$213.83	4.731%	$223.9463	$223.95	$223.95	$223.90
Purchase #3	$214.36	7.414%	$230.2527	$230.25	$230.25	$230.30
Purchase #4	$132.29	9.339%	$144.6446	$144.64	$144.65	$144.60
Purchase #5	$69.54	4.714%	$72.8181	$72.82	$72.80	$72.80
Purchase #6	$128.35	7.699%	$138.2317	$138.23	$138.25	$138.20
Purchase #7	$169.52	11.425%	$188.8877	$188.89	$188.90	$188.90
7 purchase totals =	$942.26		$1,014.6607	$1,014.66	$1,014.70	$1,014.60