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	$97.45	10.297%	$107.4844	$107.48	$107.50	$107.50
Purchase #2	$64.87	11.495%	$72.3268	$72.33	$72.35	$72.30
Purchase #3	$229.30	4.669%	$240.006	$240.01	$240.00	$240.00
Purchase #4	$119.31	12.716%	$134.4815	$134.48	$134.50	$134.50
Purchase #5	$37.28	7.674%	$40.1409	$40.14	$40.15	$40.10
Purchase #6	$70.27	4.234%	$73.2452	$73.25	$73.25	$73.20
Purchase #7	$204.54	13.170%	$231.4779	$231.48	$231.50	$231.50
7 purchase totals =	$823.02		$899.1627	$899.17	$899.25	$899.10