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	$100.76	13.720%	$114.5843	$114.58	$114.60	$114.60
Purchase #2	$138.82	10.593%	$153.5252	$153.53	$153.55	$153.50
Purchase #3	$223.34	3.847%	$231.9319	$231.93	$231.95	$231.90
Purchase #4	$67.34	11.166%	$74.8592	$74.86	$74.85	$74.90
Purchase #5	$195.83	10.832%	$217.0423	$217.04	$217.05	$217.00
Purchase #6	$176.28	11.520%	$196.5875	$196.59	$196.60	$196.60
Purchase #7	$28.88	7.278%	$30.9819	$30.98	$31.00	$31.00
7 purchase totals =	$931.25		$1,019.5123	$1,019.51	$1,019.60	$1,019.50