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	$108.58	3.679%	$112.5747	$112.57	$112.55	$112.60
Purchase #2	$243.39	12.273%	$273.2613	$273.26	$273.25	$273.30
Purchase #3	$66.65	8.792%	$72.5099	$72.51	$72.50	$72.50
Purchase #4	$100.51	6.388%	$106.9306	$106.93	$106.95	$106.90
Purchase #5	$219.76	9.227%	$240.0373	$240.04	$240.05	$240.00
Purchase #6	$123.82	10.136%	$136.3704	$136.37	$136.35	$136.40
Purchase #7	$98.52	10.314%	$108.6814	$108.68	$108.70	$108.70
7 purchase totals =	$961.23		$1,050.3656	$1,050.36	$1,050.35	$1,050.40