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	$174.45	4.633%	$182.5323	$182.53	$182.55	$182.50
Purchase #2	$69.59	13.377%	$78.8991	$78.90	$78.90	$78.90
Purchase #3	$99.42	6.811%	$106.1915	$106.19	$106.20	$106.20
Purchase #4	$38.98	5.746%	$41.2198	$41.22	$41.20	$41.20
Purchase #5	$188.70	10.381%	$208.2889	$208.29	$208.30	$208.30
Purchase #6	$107.33	13.307%	$121.6124	$121.61	$121.60	$121.60
Purchase #7	$178.72	10.146%	$196.8529	$196.85	$196.85	$196.90
7 purchase totals =	$857.19		$935.5969	$935.59	$935.60	$935.60