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	$37.98	7.520%	$40.8361	$40.84	$40.85	$40.80
Purchase #2	$229.40	3.188%	$236.7133	$236.71	$236.70	$236.70
Purchase #3	$47.89	10.559%	$52.9467	$52.95	$52.95	$52.90
Purchase #4	$177.27	10.804%	$196.4223	$196.42	$196.40	$196.40
Purchase #5	$137.84	6.253%	$146.4591	$146.46	$146.45	$146.50
Purchase #6	$189.85	7.534%	$204.1533	$204.15	$204.15	$204.20
Purchase #7	$188.35	10.355%	$207.8536	$207.85	$207.85	$207.90
7 purchase totals =	$1,008.58		$1,085.3844	$1,085.38	$1,085.35	$1,085.40