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	$100.26	5.479%	$105.7532	$105.75	$105.75	$105.80
Purchase #2	$74.27	6.236%	$78.9015	$78.90	$78.90	$78.90
Purchase #3	$59.70	4.256%	$62.2408	$62.24	$62.25	$62.20
Purchase #4	$236.63	10.182%	$260.7237	$260.72	$260.70	$260.70
Purchase #5	$94.68	7.126%	$101.4269	$101.43	$101.45	$101.40
Purchase #6	$59.49	9.454%	$65.1142	$65.11	$65.10	$65.10
Purchase #7	$113.98	3.839%	$118.3557	$118.36	$118.35	$118.40
7 purchase totals =	$739.01		$792.5160	$792.51	$792.50	$792.50