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	$44.58	6.433%	$47.4478	$47.45	$47.45	$47.40
Purchase #2	$177.40	10.715%	$196.4084	$196.41	$196.40	$196.40
Purchase #3	$45.26	8.506%	$49.1098	$49.11	$49.10	$49.10
Purchase #4	$217.71	11.653%	$243.0797	$243.08	$243.10	$243.10
Purchase #5	$198.72	9.800%	$218.1946	$218.19	$218.20	$218.20
Purchase #6	$215.59	13.669%	$245.059	$245.06	$245.05	$245.10
Purchase #7	$162.60	11.684%	$181.5982	$181.60	$181.60	$181.60
7 purchase totals =	$1,061.86		$1,180.8975	$1,180.90	$1,180.90	$1,180.90