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	$47.67	11.649%	$53.2231	$53.22	$53.20	$53.20
Purchase #2	$63.47	4.215%	$66.1453	$66.15	$66.15	$66.10
Purchase #3	$157.72	5.858%	$166.9592	$166.96	$166.95	$167.00
Purchase #4	$54.76	3.148%	$56.4838	$56.48	$56.50	$56.50
Purchase #5	$243.28	5.365%	$256.332	$256.33	$256.35	$256.30
Purchase #6	$172.46	4.742%	$180.6381	$180.64	$180.65	$180.60
Purchase #7	$167.63	12.632%	$188.805	$188.81	$188.80	$188.80
7 purchase totals =	$906.99		$968.5865	$968.59	$968.60	$968.50