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	$237.30	11.212%	$263.9061	$263.91	$263.90	$263.90
Purchase #2	$10.36	6.665%	$11.0505	$11.05	$11.05	$11.10
Purchase #3	$74.38	5.113%	$78.183	$78.18	$78.20	$78.20
Purchase #4	$60.84	8.723%	$66.1471	$66.15	$66.15	$66.10
Purchase #5	$108.85	5.317%	$114.6376	$114.64	$114.65	$114.60
Purchase #6	$90.70	9.275%	$99.1124	$99.11	$99.10	$99.10
Purchase #7	$176.34	4.495%	$184.2665	$184.27	$184.25	$184.30
7 purchase totals =	$758.77		$817.3032	$817.31	$817.30	$817.30