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	$76.56	4.133%	$79.7242	$79.72	$79.70	$79.70
Purchase #2	$117.34	4.359%	$122.4549	$122.45	$122.45	$122.50
Purchase #3	$138.47	6.424%	$147.3653	$147.37	$147.35	$147.40
Purchase #4	$211.99	3.541%	$219.4966	$219.50	$219.50	$219.50
Purchase #5	$164.59	4.221%	$171.5373	$171.54	$171.55	$171.50
Purchase #6	$233.42	9.356%	$255.2588	$255.26	$255.25	$255.30
Purchase #7	$113.42	12.719%	$127.8459	$127.85	$127.85	$127.80
7 purchase totals =	$1,055.79		$1,123.6830	$1,123.69	$1,123.65	$1,123.70