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	$229.43	7.634%	$246.9447	$246.94	$246.95	$246.90
Purchase #2	$182.89	3.609%	$189.4905	$189.49	$189.50	$189.50
Purchase #3	$61.91	9.237%	$67.6286	$67.63	$67.65	$67.60
Purchase #4	$144.95	3.633%	$150.216	$150.22	$150.20	$150.20
Purchase #5	$116.43	9.503%	$127.4943	$127.49	$127.50	$127.50
Purchase #6	$188.39	13.585%	$213.9828	$213.98	$214.00	$214.00
Purchase #7	$203.56	11.307%	$226.5765	$226.58	$226.60	$226.60
7 purchase totals =	$1,127.56		$1,222.3334	$1,222.33	$1,222.40	$1,222.30