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	$223.77	10.574%	$247.4314	$247.43	$247.45	$247.40
Purchase #2	$213.50	12.375%	$239.9206	$239.92	$239.90	$239.90
Purchase #3	$113.31	4.406%	$118.3024	$118.30	$118.30	$118.30
Purchase #4	$225.25	7.391%	$241.8982	$241.90	$241.90	$241.90
Purchase #5	$46.56	3.777%	$48.3186	$48.32	$48.30	$48.30
Purchase #6	$72.74	7.259%	$78.0202	$78.02	$78.00	$78.00
Purchase #7	$118.67	7.354%	$127.397	$127.40	$127.40	$127.40
7 purchase totals =	$1,013.80		$1,101.2884	$1,101.29	$1,101.25	$1,101.20