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	$106.54	10.548%	$117.7778	$117.78	$117.80	$117.80
Purchase #2	$72.97	6.335%	$77.5926	$77.59	$77.60	$77.60
Purchase #3	$214.82	10.219%	$236.7725	$236.77	$236.75	$236.80
Purchase #4	$88.86	13.604%	$100.9485	$100.95	$100.95	$100.90
Purchase #5	$250.57	9.420%	$274.1737	$274.17	$274.15	$274.20
Purchase #6	$91.53	11.780%	$102.3122	$102.31	$102.30	$102.30
Purchase #7	$115.45	6.765%	$123.2602	$123.26	$123.25	$123.30
7 purchase totals =	$940.74		$1,032.8375	$1,032.83	$1,032.80	$1,032.90