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	$189.30	3.553%	$196.0258	$196.03	$196.05	$196.00
Purchase #2	$74.91	4.286%	$78.1206	$78.12	$78.10	$78.10
Purchase #3	$133.78	12.648%	$150.7005	$150.70	$150.70	$150.70
Purchase #4	$105.89	9.832%	$116.3011	$116.30	$116.30	$116.30
Purchase #5	$78.76	13.651%	$89.5115	$89.51	$89.50	$89.50
Purchase #6	$95.33	7.631%	$102.6046	$102.60	$102.60	$102.60
Purchase #7	$217.28	13.273%	$246.1196	$246.12	$246.10	$246.10
7 purchase totals =	$895.25		$979.3837	$979.38	$979.35	$979.30