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	$200.40	13.532%	$227.5181	$227.52	$227.50	$227.50
Purchase #2	$71.55	8.864%	$77.8922	$77.89	$77.90	$77.90
Purchase #3	$131.98	9.250%	$144.1882	$144.19	$144.20	$144.20
Purchase #4	$69.69	12.323%	$78.2779	$78.28	$78.30	$78.30
Purchase #5	$111.98	13.579%	$127.1858	$127.19	$127.20	$127.20
Purchase #6	$189.35	6.387%	$201.4438	$201.44	$201.45	$201.40
Purchase #7	$222.30	5.136%	$233.7173	$233.72	$233.70	$233.70
7 purchase totals =	$997.25		$1,090.2233	$1,090.23	$1,090.25	$1,090.20