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	$61.40	7.197%	$65.819	$65.82	$65.80	$65.80
Purchase #2	$69.72	3.767%	$72.3464	$72.35	$72.35	$72.30
Purchase #3	$114.55	5.497%	$120.8468	$120.85	$120.85	$120.80
Purchase #4	$235.47	6.768%	$251.4066	$251.41	$251.40	$251.40
Purchase #5	$86.70	11.184%	$96.3965	$96.40	$96.40	$96.40
Purchase #6	$238.45	10.770%	$264.1311	$264.13	$264.15	$264.10
Purchase #7	$35.43	9.773%	$38.8926	$38.89	$38.90	$38.90
7 purchase totals =	$841.72		$909.8390	$909.85	$909.85	$909.70