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	$220.42	7.676%	$237.3394	$237.34	$237.35	$237.30
Purchase #2	$149.56	4.739%	$156.6476	$156.65	$156.65	$156.60
Purchase #3	$46.99	11.617%	$52.4488	$52.45	$52.45	$52.40
Purchase #4	$246.47	5.322%	$259.5871	$259.59	$259.60	$259.60
Purchase #5	$89.80	11.367%	$100.0076	$100.01	$100.00	$100.00
Purchase #6	$127.28	11.624%	$142.075	$142.08	$142.10	$142.10
Purchase #7	$104.80	10.292%	$115.586	$115.59	$115.60	$115.60
7 purchase totals =	$985.32		$1,063.6915	$1,063.71	$1,063.75	$1,063.60