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	$159.50	4.779%	$167.1225	$167.12	$167.10	$167.10
Purchase #2	$52.35	4.435%	$54.6717	$54.67	$54.65	$54.70
Purchase #3	$102.57	11.699%	$114.5697	$114.57	$114.55	$114.60
Purchase #4	$204.81	6.574%	$218.2742	$218.27	$218.25	$218.30
Purchase #5	$13.49	7.715%	$14.5308	$14.53	$14.55	$14.50
Purchase #6	$95.28	4.212%	$99.2932	$99.29	$99.30	$99.30
Purchase #7	$137.76	9.597%	$150.9808	$150.98	$151.00	$151.00
7 purchase totals =	$765.76		$819.4429	$819.43	$819.40	$819.50