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	$56.33	11.529%	$62.8243	$62.82	$62.80	$62.80
Purchase #2	$82.73	3.513%	$85.6363	$85.64	$85.65	$85.60
Purchase #3	$173.66	13.104%	$196.4164	$196.42	$196.40	$196.40
Purchase #4	$142.38	6.414%	$151.5123	$151.51	$151.50	$151.50
Purchase #5	$43.28	3.811%	$44.9294	$44.93	$44.95	$44.90
Purchase #6	$139.58	6.599%	$148.7909	$148.79	$148.80	$148.80
Purchase #7	$218.32	4.313%	$227.7361	$227.74	$227.75	$227.70
7 purchase totals =	$856.28		$917.8457	$917.85	$917.85	$917.70