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	$199.62	12.301%	$224.1753	$224.18	$224.20	$224.20
Purchase #2	$135.45	13.268%	$153.4215	$153.42	$153.40	$153.40
Purchase #3	$68.27	5.836%	$72.2542	$72.25	$72.25	$72.30
Purchase #4	$78.54	8.400%	$85.1374	$85.14	$85.15	$85.10
Purchase #5	$161.81	6.822%	$172.8487	$172.85	$172.85	$172.80
Purchase #6	$191.72	7.492%	$206.0837	$206.08	$206.10	$206.10
Purchase #7	$176.65	13.254%	$200.0632	$200.06	$200.05	$200.10
7 purchase totals =	$1,012.06		$1,113.9840	$1,113.98	$1,114.00	$1,114.00