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	$53.30	4.524%	$55.7113	$55.71	$55.70	$55.70
Purchase #2	$182.68	9.637%	$200.2849	$200.28	$200.30	$200.30
Purchase #3	$37.42	9.111%	$40.8293	$40.83	$40.85	$40.80
Purchase #4	$162.70	12.712%	$183.3824	$183.38	$183.40	$183.40
Purchase #5	$187.29	13.710%	$212.9675	$212.97	$212.95	$213.00
Purchase #6	$128.45	10.738%	$142.243	$142.24	$142.25	$142.20
Purchase #7	$156.40	3.634%	$162.0836	$162.08	$162.10	$162.10
7 purchase totals =	$908.24		$997.5020	$997.49	$997.55	$997.50