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	$193.54	10.766%	$214.3765	$214.38	$214.40	$214.40
Purchase #2	$113.61	13.836%	$129.3291	$129.33	$129.35	$129.30
Purchase #3	$133.48	7.256%	$143.1653	$143.17	$143.15	$143.20
Purchase #4	$74.53	4.853%	$78.1469	$78.15	$78.15	$78.10
Purchase #5	$80.94	11.760%	$90.4585	$90.46	$90.45	$90.50
Purchase #6	$38.57	10.691%	$42.6935	$42.69	$42.70	$42.70
Purchase #7	$31.84	6.738%	$33.9854	$33.99	$34.00	$34.00
7 purchase totals =	$666.51		$732.1552	$732.17	$732.20	$732.20