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	$56.25	11.640%	$62.7975	$62.80	$62.80	$62.80
Purchase #2	$146.43	13.671%	$166.4484	$166.45	$166.45	$166.40
Purchase #3	$206.93	4.309%	$215.8466	$215.85	$215.85	$215.80
Purchase #4	$70.43	10.242%	$77.6434	$77.64	$77.65	$77.60
Purchase #5	$243.63	6.525%	$259.5269	$259.53	$259.55	$259.50
Purchase #6	$168.42	11.825%	$188.3357	$188.34	$188.35	$188.30
Purchase #7	$187.45	4.640%	$196.1477	$196.15	$196.15	$196.10
7 purchase totals =	$1,079.54		$1,166.7462	$1,166.76	$1,166.80	$1,166.50