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	$147.58	11.235%	$164.1606	$164.16	$164.15	$164.20
Purchase #2	$126.38	12.802%	$142.5592	$142.56	$142.55	$142.60
Purchase #3	$87.50	9.483%	$95.7976	$95.80	$95.80	$95.80
Purchase #4	$158.51	6.245%	$168.4089	$168.41	$168.40	$168.40
Purchase #5	$112.89	13.229%	$127.8242	$127.82	$127.80	$127.80
Purchase #6	$75.76	12.173%	$84.9823	$84.98	$85.00	$85.00
Purchase #7	$42.60	4.866%	$44.6729	$44.67	$44.65	$44.70
7 purchase totals =	$751.22		$828.4057	$828.40	$828.35	$828.50