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	$162.41	7.696%	$174.9091	$174.91	$174.90	$174.90
Purchase #2	$153.41	13.423%	$174.0022	$174.00	$174.00	$174.00
Purchase #3	$130.82	9.693%	$143.5004	$143.50	$143.50	$143.50
Purchase #4	$214.27	4.851%	$224.6642	$224.66	$224.65	$224.70
Purchase #5	$156.69	8.386%	$169.83	$169.83	$169.85	$169.80
Purchase #6	$16.65	13.335%	$18.8703	$18.87	$18.85	$18.90
Purchase #7	$184.38	5.309%	$194.1687	$194.17	$194.15	$194.20
7 purchase totals =	$1,018.63		$1,099.9449	$1,099.94	$1,099.90	$1,100.00