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	$231.92	12.364%	$260.5946	$260.59	$260.60	$260.60
Purchase #2	$145.90	3.756%	$151.38	$151.38	$151.40	$151.40
Purchase #3	$221.90	7.874%	$239.3724	$239.37	$239.35	$239.40
Purchase #4	$171.79	11.471%	$191.496	$191.50	$191.50	$191.50
Purchase #5	$110.45	5.805%	$116.8616	$116.86	$116.85	$116.90
Purchase #6	$16.96	3.867%	$17.6158	$17.62	$17.60	$17.60
Purchase #7	$69.34	4.178%	$72.237	$72.24	$72.25	$72.20
7 purchase totals =	$968.26		$1,049.5574	$1,049.56	$1,049.55	$1,049.60