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	$76.50	12.668%	$86.191	$86.19	$86.20	$86.20
Purchase #2	$21.72	4.841%	$22.7715	$22.77	$22.75	$22.80
Purchase #3	$225.45	4.724%	$236.1003	$236.10	$236.10	$236.10
Purchase #4	$106.59	3.137%	$109.9337	$109.93	$109.95	$109.90
Purchase #5	$247.42	9.336%	$270.5191	$270.52	$270.50	$270.50
Purchase #6	$100.47	4.581%	$105.0725	$105.07	$105.05	$105.10
Purchase #7	$158.83	9.837%	$174.4541	$174.45	$174.45	$174.50
7 purchase totals =	$936.98		$1,005.0422	$1,005.03	$1,005.00	$1,005.10