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	$42.87	4.815%	$44.9342	$44.93	$44.95	$44.90
Purchase #2	$184.65	10.483%	$204.0069	$204.01	$204.00	$204.00
Purchase #3	$150.76	13.850%	$171.6403	$171.64	$171.65	$171.60
Purchase #4	$158.72	9.846%	$174.3476	$174.35	$174.35	$174.30
Purchase #5	$65.47	6.648%	$69.8224	$69.82	$69.80	$69.80
Purchase #6	$222.65	6.585%	$237.3115	$237.31	$237.30	$237.30
Purchase #7	$175.47	5.762%	$185.5806	$185.58	$185.60	$185.60
7 purchase totals =	$1,000.59		$1,087.6435	$1,087.64	$1,087.65	$1,087.50