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	$93.29	12.822%	$105.2516	$105.25	$105.25	$105.30
Purchase #2	$231.48	13.724%	$263.2483	$263.25	$263.25	$263.20
Purchase #3	$198.50	9.197%	$216.756	$216.76	$216.75	$216.80
Purchase #4	$237.35	4.746%	$248.6146	$248.61	$248.60	$248.60
Purchase #5	$101.58	4.349%	$105.9977	$106.00	$106.00	$106.00
Purchase #6	$130.26	6.751%	$139.0539	$139.05	$139.05	$139.10
Purchase #7	$56.63	10.565%	$62.613	$62.61	$62.60	$62.60
7 purchase totals =	$1,049.09		$1,141.5351	$1,141.53	$1,141.50	$1,141.60