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	$64.50	12.288%	$72.4258	$72.43	$72.45	$72.40
Purchase #2	$127.38	9.391%	$139.3423	$139.34	$139.35	$139.30
Purchase #3	$92.68	5.413%	$97.6968	$97.70	$97.70	$97.70
Purchase #4	$55.46	7.109%	$59.4027	$59.40	$59.40	$59.40
Purchase #5	$211.77	10.452%	$233.9042	$233.90	$233.90	$233.90
Purchase #6	$28.46	9.748%	$31.2343	$31.23	$31.25	$31.20
Purchase #7	$154.71	5.441%	$163.1278	$163.13	$163.15	$163.10
7 purchase totals =	$734.96		$797.1339	$797.13	$797.20	$797.00