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	$42.59	13.515%	$48.346	$48.35	$48.35	$48.30
Purchase #2	$59.92	4.683%	$62.7261	$62.73	$62.75	$62.70
Purchase #3	$206.25	5.293%	$217.1668	$217.17	$217.15	$217.20
Purchase #4	$208.45	9.110%	$227.4398	$227.44	$227.45	$227.40
Purchase #5	$214.77	7.669%	$231.2407	$231.24	$231.25	$231.20
Purchase #6	$80.47	11.411%	$89.6524	$89.65	$89.65	$89.70
Purchase #7	$65.59	12.353%	$73.6923	$73.69	$73.70	$73.70
7 purchase totals =	$878.04		$950.2641	$950.27	$950.30	$950.20