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	$198.51	7.373%	$213.1461	$213.15	$213.15	$213.10
Purchase #2	$231.84	5.469%	$244.5193	$244.52	$244.50	$244.50
Purchase #3	$84.29	8.618%	$91.5541	$91.55	$91.55	$91.60
Purchase #4	$240.91	13.229%	$272.78	$272.78	$272.80	$272.80
Purchase #5	$78.32	5.750%	$82.8234	$82.82	$82.80	$82.80
Purchase #6	$115.71	10.484%	$127.841	$127.84	$127.85	$127.80
Purchase #7	$37.32	3.522%	$38.6344	$38.63	$38.65	$38.60
7 purchase totals =	$986.90		$1,071.2983	$1,071.29	$1,071.30	$1,071.20