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	$220.62	4.827%	$231.2693	$231.27	$231.25	$231.30
Purchase #2	$104.48	6.708%	$111.4885	$111.49	$111.50	$111.50
Purchase #3	$196.85	3.398%	$203.539	$203.54	$203.55	$203.50
Purchase #4	$245.85	13.699%	$279.529	$279.53	$279.55	$279.50
Purchase #5	$128.28	5.104%	$134.8274	$134.83	$134.85	$134.80
Purchase #6	$55.98	12.495%	$62.9747	$62.97	$62.95	$63.00
Purchase #7	$137.96	4.736%	$144.4938	$144.49	$144.50	$144.50
7 purchase totals =	$1,090.02		$1,168.1217	$1,168.12	$1,168.15	$1,168.10