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	$176.60	12.394%	$198.4878	$198.49	$198.50	$198.50
Purchase #2	$74.30	6.186%	$78.8962	$78.90	$78.90	$78.90
Purchase #3	$116.51	3.255%	$120.3024	$120.30	$120.30	$120.30
Purchase #4	$165.45	13.724%	$188.1564	$188.16	$188.15	$188.20
Purchase #5	$123.62	13.402%	$140.1876	$140.19	$140.20	$140.20
Purchase #6	$170.25	13.283%	$192.8643	$192.86	$192.85	$192.90
Purchase #7	$181.83	5.292%	$191.4524	$191.45	$191.45	$191.50
7 purchase totals =	$1,008.56		$1,110.3471	$1,110.35	$1,110.35	$1,110.50