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	$179.33	10.835%	$198.7604	$198.76	$198.75	$198.80
Purchase #2	$29.43	12.382%	$33.074	$33.07	$33.05	$33.10
Purchase #3	$37.69	4.768%	$39.4871	$39.49	$39.50	$39.50
Purchase #4	$130.50	9.316%	$142.6574	$142.66	$142.65	$142.70
Purchase #5	$49.28	3.769%	$51.1374	$51.14	$51.15	$51.10
Purchase #6	$196.61	10.482%	$217.2187	$217.22	$217.20	$217.20
Purchase #7	$246.77	3.837%	$256.2386	$256.24	$256.25	$256.20
7 purchase totals =	$869.61		$938.5736	$938.58	$938.55	$938.60