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	$57.73	6.691%	$61.5927	$61.59	$61.60	$61.60
Purchase #2	$177.92	3.701%	$184.5048	$184.50	$184.50	$184.50
Purchase #3	$139.82	10.731%	$154.8241	$154.82	$154.80	$154.80
Purchase #4	$138.82	10.398%	$153.2545	$153.25	$153.25	$153.30
Purchase #5	$178.93	7.609%	$192.5448	$192.54	$192.55	$192.50
Purchase #6	$91.41	8.525%	$99.2027	$99.20	$99.20	$99.20
Purchase #7	$152.85	5.738%	$161.6205	$161.62	$161.60	$161.60
7 purchase totals =	$937.48		$1,007.5441	$1,007.52	$1,007.50	$1,007.50