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	$214.67	12.528%	$241.5639	$241.56	$241.55	$241.60
Purchase #2	$123.84	13.509%	$140.5695	$140.57	$140.55	$140.60
Purchase #3	$53.40	10.480%	$58.9963	$59.00	$59.00	$59.00
Purchase #4	$117.56	11.220%	$130.7502	$130.75	$130.75	$130.80
Purchase #5	$97.81	5.505%	$103.1944	$103.19	$103.20	$103.20
Purchase #6	$222.76	7.841%	$240.2266	$240.23	$240.25	$240.20
Purchase #7	$212.75	13.321%	$241.0904	$241.09	$241.10	$241.10
7 purchase totals =	$1,042.79		$1,156.3913	$1,156.39	$1,156.40	$1,156.50