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	$41.34	3.336%	$42.7191	$42.72	$42.70	$42.70
Purchase #2	$110.75	12.245%	$124.3113	$124.31	$124.30	$124.30
Purchase #3	$37.81	12.300%	$42.4606	$42.46	$42.45	$42.50
Purchase #4	$206.38	4.115%	$214.8725	$214.87	$214.85	$214.90
Purchase #5	$103.87	3.828%	$107.8461	$107.85	$107.85	$107.80
Purchase #6	$213.96	7.650%	$230.3279	$230.33	$230.35	$230.30
Purchase #7	$248.82	8.316%	$269.5119	$269.51	$269.50	$269.50
7 purchase totals =	$962.93		$1,032.0494	$1,032.05	$1,032.00	$1,032.00