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	$174.56	4.196%	$181.8845	$181.88	$181.90	$181.90
Purchase #2	$132.91	11.832%	$148.6359	$148.64	$148.65	$148.60
Purchase #3	$79.70	4.429%	$83.2299	$83.23	$83.25	$83.20
Purchase #4	$238.64	10.288%	$263.1913	$263.19	$263.20	$263.20
Purchase #5	$197.95	13.848%	$225.3621	$225.36	$225.35	$225.40
Purchase #6	$29.54	6.503%	$31.461	$31.46	$31.45	$31.50
Purchase #7	$111.56	4.317%	$116.376	$116.38	$116.40	$116.40
7 purchase totals =	$964.86		$1,050.1407	$1,050.14	$1,050.20	$1,050.20