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	$234.57	13.279%	$265.7186	$265.72	$265.70	$265.70
Purchase #2	$35.56	6.851%	$37.9962	$38.00	$38.00	$38.00
Purchase #3	$216.66	8.829%	$235.7889	$235.79	$235.80	$235.80
Purchase #4	$80.39	12.572%	$90.4966	$90.50	$90.50	$90.50
Purchase #5	$46.98	9.781%	$51.5751	$51.58	$51.60	$51.60
Purchase #6	$149.65	6.257%	$159.0136	$159.01	$159.00	$159.00
Purchase #7	$169.54	3.660%	$175.7452	$175.75	$175.75	$175.70
7 purchase totals =	$933.35		$1,016.3342	$1,016.35	$1,016.35	$1,016.30