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	$176.78	3.244%	$182.5147	$182.51	$182.50	$182.50
Purchase #2	$40.97	5.387%	$43.1771	$43.18	$43.20	$43.20
Purchase #3	$128.62	11.280%	$143.1283	$143.13	$143.15	$143.10
Purchase #4	$49.73	4.377%	$51.9067	$51.91	$51.90	$51.90
Purchase #5	$162.53	6.740%	$173.4845	$173.48	$173.50	$173.50
Purchase #6	$105.89	13.438%	$120.1195	$120.12	$120.10	$120.10
Purchase #7	$238.41	12.853%	$269.0528	$269.05	$269.05	$269.10
7 purchase totals =	$902.93		$983.3836	$983.38	$983.40	$983.40