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	$137.43	10.330%	$151.6265	$151.63	$151.65	$151.60
Purchase #2	$250.65	12.313%	$281.5125	$281.51	$281.50	$281.50
Purchase #3	$165.80	6.819%	$177.1059	$177.11	$177.10	$177.10
Purchase #4	$46.40	11.185%	$51.5898	$51.59	$51.60	$51.60
Purchase #5	$123.26	8.393%	$133.6052	$133.61	$133.60	$133.60
Purchase #6	$176.83	7.767%	$190.5644	$190.56	$190.55	$190.60
Purchase #7	$113.32	10.719%	$125.4668	$125.47	$125.45	$125.50
7 purchase totals =	$1,013.69		$1,111.4711	$1,111.48	$1,111.45	$1,111.50