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	$207.40	5.842%	$219.5163	$219.52	$219.50	$219.50
Purchase #2	$122.32	12.388%	$137.473	$137.47	$137.45	$137.50
Purchase #3	$180.88	4.158%	$188.401	$188.40	$188.40	$188.40
Purchase #4	$156.80	7.739%	$168.9348	$168.93	$168.95	$168.90
Purchase #5	$212.44	12.297%	$238.5637	$238.56	$238.55	$238.60
Purchase #6	$44.55	6.700%	$47.5349	$47.53	$47.55	$47.50
Purchase #7	$75.44	3.509%	$78.0872	$78.09	$78.10	$78.10
7 purchase totals =	$999.83		$1,078.5109	$1,078.50	$1,078.50	$1,078.50