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	$112.63	12.775%	$127.0185	$127.02	$127.00	$127.00
Purchase #2	$174.67	7.278%	$187.3825	$187.38	$187.40	$187.40
Purchase #3	$36.50	11.216%	$40.5938	$40.59	$40.60	$40.60
Purchase #4	$45.69	7.132%	$48.9486	$48.95	$48.95	$48.90
Purchase #5	$149.27	13.477%	$169.3871	$169.39	$169.40	$169.40
Purchase #6	$176.98	12.128%	$198.4441	$198.44	$198.45	$198.40
Purchase #7	$11.50	8.571%	$12.4857	$12.49	$12.50	$12.50
7 purchase totals =	$707.24		$784.2603	$784.26	$784.30	$784.20