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	$134.41	5.200%	$141.3993	$141.40	$141.40	$141.40
Purchase #2	$165.80	3.831%	$172.1518	$172.15	$172.15	$172.20
Purchase #3	$48.83	13.509%	$55.4264	$55.43	$55.45	$55.40
Purchase #4	$157.82	6.481%	$168.0483	$168.05	$168.05	$168.00
Purchase #5	$113.31	8.624%	$123.0819	$123.08	$123.10	$123.10
Purchase #6	$159.25	13.295%	$180.4223	$180.42	$180.40	$180.40
Purchase #7	$213.83	10.360%	$235.9828	$235.98	$236.00	$236.00
7 purchase totals =	$993.25		$1,076.5128	$1,076.51	$1,076.55	$1,076.50