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	$172.54	5.172%	$181.4638	$181.46	$181.45	$181.50
Purchase #2	$236.33	13.587%	$268.4402	$268.44	$268.45	$268.40
Purchase #3	$173.64	10.760%	$192.3237	$192.32	$192.30	$192.30
Purchase #4	$54.84	3.299%	$56.6492	$56.65	$56.65	$56.60
Purchase #5	$241.96	12.541%	$272.3042	$272.30	$272.30	$272.30
Purchase #6	$232.75	12.801%	$262.5443	$262.54	$262.55	$262.50
Purchase #7	$86.28	4.125%	$89.8391	$89.84	$89.85	$89.80
7 purchase totals =	$1,198.34		$1,323.5645	$1,323.55	$1,323.55	$1,323.40