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	$163.70	10.472%	$180.8427	$180.84	$180.85	$180.80
Purchase #2	$120.84	8.573%	$131.1996	$131.20	$131.20	$131.20
Purchase #3	$83.83	10.161%	$92.348	$92.35	$92.35	$92.30
Purchase #4	$176.74	11.245%	$196.6144	$196.61	$196.60	$196.60
Purchase #5	$16.32	12.635%	$18.382	$18.38	$18.40	$18.40
Purchase #6	$30.28	5.430%	$31.9242	$31.92	$31.90	$31.90
Purchase #7	$72.36	11.371%	$80.5881	$80.59	$80.60	$80.60
7 purchase totals =	$664.07		$731.8990	$731.89	$731.90	$731.80