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	$135.99	5.664%	$143.6925	$143.69	$143.70	$143.70
Purchase #2	$158.29	13.863%	$180.2337	$180.23	$180.25	$180.20
Purchase #3	$61.27	9.616%	$67.1617	$67.16	$67.15	$67.20
Purchase #4	$175.76	3.856%	$182.5373	$182.54	$182.55	$182.50
Purchase #5	$34.27	10.421%	$37.8413	$37.84	$37.85	$37.80
Purchase #6	$142.34	9.156%	$155.3727	$155.37	$155.35	$155.40
Purchase #7	$158.45	12.506%	$178.2658	$178.27	$178.25	$178.30
7 purchase totals =	$866.37		$945.1050	$945.10	$945.10	$945.10