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	$182.59	4.314%	$190.4669	$190.47	$190.45	$190.50
Purchase #2	$55.61	3.466%	$57.5374	$57.54	$57.55	$57.50
Purchase #3	$93.72	12.786%	$105.703	$105.70	$105.70	$105.70
Purchase #4	$151.32	5.618%	$159.8212	$159.82	$159.80	$159.80
Purchase #5	$238.27	10.781%	$263.9579	$263.96	$263.95	$264.00
Purchase #6	$99.73	5.550%	$105.265	$105.27	$105.25	$105.30
Purchase #7	$153.76	5.309%	$161.9231	$161.92	$161.90	$161.90
7 purchase totals =	$975.00		$1,044.6745	$1,044.68	$1,044.60	$1,044.70