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	$177.29	4.715%	$185.6492	$185.65	$185.65	$185.60
Purchase #2	$49.30	8.599%	$53.5393	$53.54	$53.55	$53.50
Purchase #3	$38.72	12.609%	$43.6022	$43.60	$43.60	$43.60
Purchase #4	$199.62	8.162%	$215.913	$215.91	$215.90	$215.90
Purchase #5	$124.69	11.297%	$138.7762	$138.78	$138.80	$138.80
Purchase #6	$75.72	13.630%	$86.0406	$86.04	$86.05	$86.00
Purchase #7	$233.51	5.219%	$245.6969	$245.70	$245.70	$245.70
7 purchase totals =	$898.85		$969.2174	$969.22	$969.25	$969.10