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	$227.77	5.426%	$240.1288	$240.13	$240.15	$240.10
Purchase #2	$74.60	5.651%	$78.8156	$78.82	$78.80	$78.80
Purchase #3	$126.45	8.227%	$136.853	$136.85	$136.85	$136.90
Purchase #4	$127.56	5.723%	$134.8603	$134.86	$134.85	$134.90
Purchase #5	$47.63	11.508%	$53.1113	$53.11	$53.10	$53.10
Purchase #6	$141.75	11.212%	$157.643	$157.64	$157.65	$157.60
Purchase #7	$220.69	11.657%	$246.4158	$246.42	$246.40	$246.40
7 purchase totals =	$966.45		$1,047.8278	$1,047.83	$1,047.80	$1,047.80