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	$124.81	4.389%	$130.2879	$130.29	$130.30	$130.30
Purchase #2	$169.58	11.163%	$188.5102	$188.51	$188.50	$188.50
Purchase #3	$12.53	4.780%	$13.1289	$13.13	$13.15	$13.10
Purchase #4	$12.49	5.670%	$13.1982	$13.20	$13.20	$13.20
Purchase #5	$104.63	11.711%	$116.8832	$116.88	$116.90	$116.90
Purchase #6	$41.33	6.160%	$43.8759	$43.88	$43.90	$43.90
Purchase #7	$231.60	3.838%	$240.4888	$240.49	$240.50	$240.50
7 purchase totals =	$696.97		$746.3731	$746.38	$746.45	$746.40