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	$54.99	11.537%	$61.3342	$61.33	$61.35	$61.30
Purchase #2	$107.66	5.141%	$113.1948	$113.19	$113.20	$113.20
Purchase #3	$60.33	13.640%	$68.559	$68.56	$68.55	$68.60
Purchase #4	$105.79	11.337%	$117.7834	$117.78	$117.80	$117.80
Purchase #5	$169.69	9.574%	$185.9361	$185.94	$185.95	$185.90
Purchase #6	$117.51	11.613%	$131.1564	$131.16	$131.15	$131.20
Purchase #7	$94.78	10.688%	$104.9101	$104.91	$104.90	$104.90
7 purchase totals =	$710.75		$782.8740	$782.87	$782.90	$782.90