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	$113.50	8.509%	$123.1577	$123.16	$123.15	$123.20
Purchase #2	$192.48	7.275%	$206.4829	$206.48	$206.50	$206.50
Purchase #3	$166.91	7.572%	$179.5484	$179.55	$179.55	$179.50
Purchase #4	$210.50	6.154%	$223.4542	$223.45	$223.45	$223.50
Purchase #5	$85.59	12.240%	$96.0662	$96.07	$96.05	$96.10
Purchase #6	$173.98	3.704%	$180.4242	$180.42	$180.40	$180.40
Purchase #7	$126.29	12.555%	$142.1457	$142.15	$142.15	$142.10
7 purchase totals =	$1,069.25		$1,151.2793	$1,151.28	$1,151.25	$1,151.30