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	$126.55	3.117%	$130.4946	$130.49	$130.50	$130.50
Purchase #2	$168.96	8.406%	$183.1628	$183.16	$183.15	$183.20
Purchase #3	$149.93	11.740%	$167.5318	$167.53	$167.55	$167.50
Purchase #4	$116.87	5.789%	$123.6356	$123.64	$123.65	$123.60
Purchase #5	$47.61	11.690%	$53.1756	$53.18	$53.20	$53.20
Purchase #6	$34.59	4.141%	$36.0224	$36.02	$36.00	$36.00
Purchase #7	$142.49	7.469%	$153.1326	$153.13	$153.15	$153.10
7 purchase totals =	$787.00		$847.1554	$847.15	$847.20	$847.10